Rename coredump_exit_mm to coredump_task_exit and call it from do_exit
before PTRACE_EVENT_EXIT, and before any cleanup work for a task
happens.  This ensures that an accurate copy of the process can be
captured in the coredump as no cleanup for the process happens before
the coredump completes.  This also ensures that PTRACE_EVENT_EXIT
will not be visited by any thread until the coredump is complete.

Add a new flag PF_POSTCOREDUMP so that tasks that have passed through
coredump_task_exit can be recognized and ignored in zap_process.

Now that all of the coredumping happens before exit_mm remove code to
test for a coredump in progress from mm_release.

Replace "may_ptrace_stop()" with a simple test of "current->ptrace".
The other tests in may_ptrace_stop all concern avoiding stopping
during a coredump.  These tests are no longer necessary as it is now
guaranteed that fatal_signal_pending will be set if the code enters
ptrace_stop during a coredump.  The code in ptrace_stop is guaranteed
not to stop if fatal_signal_pending returns true.

Until this change "ptrace_event(PTRACE_EVENT_EXIT)" could call
ptrace_stop without fatal_signal_pending being true, as signals are
dequeued in get_signal before calling do_exit.  This is no longer
an issue as "ptrace_event(PTRACE_EVENT_EXIT)" is no longer reached
until after the coredump completes.

Link: https://lkml.kernel.org/r/874kaax26c.fsf@disp2133Reviewed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Both arch_ptrace_stop_needed and arch_ptrace_stop are called with an
exit_code and a siginfo structure.  Neither argument is used by any of
the implementations so just remove the unneeded arguments.

The two arechitectures that implement arch_ptrace_stop are ia64 and
sparc.  Both architectures flush their register stacks before a
ptrace_stack so that all of the register information can be accessed
by debuggers.

As the question of if a register stack needs to be flushed is
independent of why ptrace is stopping not needing arguments make sense.

Cc: David Miller <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Link: https://lkml.kernel.org/r/87lf3mx290.fsf@disp2133Reviewed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Dave stumbled over the incomplete and confusing documentation of the CPU
hotplug API.

Rewrite it, add the missing function documentations and correct the
existing ones.
Reported-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210909123212.489059409@linutronix.de

No users in tree use the deprecated CPU-hotplug functions anymore.

Remove them.
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210803141621.780504-39-bigeasy@linutronix.de

Rename xbc_node_find_child() to xbc_node_find_subkey() for
clarifying that function returns a key node (no value node).
Since there are xbc_node_for_each_child() (loop on all child
nodes) and xbc_node_for_each_subkey() (loop on only subkey
nodes), this name distinction is necessary to avoid confusing
users.

Link: https://lkml.kernel.org/r/163119459826.161018.11200274779483115300.stgit@devnote2Signed-off-by: NMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

Print to the trace log before releasing the lock to avoid racing with
other trace log printers of the same lock type.

Link: https://lkml.kernel.org/r/20210903022041.1843024-1-Liam.Howlett@oracle.comSigned-off-by: NLiam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michel Lespinasse <walken.cr@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

After fork, the child process will get incorrect (2x) hugetlb_usage.  If
a process uses 5 2MB hugetlb pages in an anonymous mapping,

	HugetlbPages:	   10240 kB

and then forks, the child will show,

	HugetlbPages:	   20480 kB

The reason for double the amount is because hugetlb_usage will be copied
from the parent and then increased when we copy page tables from parent
to child.  Child will have 2x actual usage.

Fix this by adding hugetlb_count_init in mm_init.

Link: https://lkml.kernel.org/r/20210826071742.877-1-liuzixian4@huawei.com
Fixes: 5d317b2b ("mm: hugetlb: proc: add HugetlbPages field to /proc/PID/status")
Signed-off-by: NLiu Zixian <liuzixian4@huawei.com>
Reviewed-by: NNaoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Clang 14 will add support for __attribute__((__error__(""))) and
__attribute__((__warning__(""))). To make use of these in
__compiletime_error and __compiletime_warning (as used by BUILD_BUG and
friends) for newer clang and detect/fallback for older versions of
clang, move these to compiler_attributes.h and guard them with
__has_attribute preprocessor guards.

Link: https://reviews.llvm.org/D106030
Link: https://bugs.llvm.org/show_bug.cgi?id=16428
Link: https://github.com/ClangBuiltLinux/linux/issues/1173Signed-off-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
[Reworded, landed in Clang 14]
Signed-off-by: NMiguel Ojeda <ojeda@kernel.org>

All users of compat_alloc_user_space() and copy_in_user() have been
removed from the kernel, only a few functions in sparc remain that can be
changed to calling arch_copy_in_user() instead.

Link: https://lkml.kernel.org/r/20210727144859.4150043-7-arnd@kernel.orgSigned-off-by: NArnd Bergmann <arnd@arndb.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

These are all handled correctly when calling the native system call entry
point, so remove the special cases.

Link: https://lkml.kernel.org/r/20210727144859.4150043-6-arnd@kernel.orgSigned-off-by: NArnd Bergmann <arnd@arndb.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The compat implementations for mbind, get_mempolicy, set_mempolicy and
migrate_pages are just there to handle the subtly different layout of
bitmaps on 32-bit hosts.

The compat implementation however lacks some of the checks that are
present in the native one, in particular for checking that the extra bits
are all zero when user space has a larger mask size than the kernel.
Worse, those extra bits do not get cleared when copying in or out of the
kernel, which can lead to incorrect data as well.

Unify the implementation to handle the compat bitmap layout directly in
the get_nodes() and copy_nodes_to_user() helpers.  Splitting out the
get_bitmap() helper from get_nodes() also helps readability of the native
case.

On x86, two additional problems are addressed by this: compat tasks can
pass a bitmap at the end of a mapping, causing a fault when reading across
the page boundary for a 64-bit word.  x32 tasks might also run into
problems with get_mempolicy corrupting data when an odd number of 32-bit
words gets passed.

On parisc the migrate_pages() system call apparently had the wrong calling
convention, as big-endian architectures expect the words inside of a
bitmap to be swapped.  This is not a problem though since parisc has no
NUMA support.

[arnd@arndb.de: fix mempolicy crash]
  Link: https://lkml.kernel.org/r/20210730143417.3700653-1-arnd@kernel.org
  Link: https://lore.kernel.org/lkml/YQPLG20V3dmOfq3a@osiris/

Link: https://lkml.kernel.org/r/20210727144859.4150043-5-arnd@kernel.orgSigned-off-by: NArnd Bergmann <arnd@arndb.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

pidmap_init() has already been replaced with pid_idr_init() in the commit
95846ecf ("pid: replace pid bitmap implementation with IDR API").
Cleanup the stale comment which still mentions it.

Link: https://lkml.kernel.org/r/20210714120713.19825-1-itazur@amazon.comSigned-off-by: NTakahiro Itazuri <itazur@amazon.com>
Cc: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This counter tracks the number of watches a user has, to compare against
the 'max_user_watches' limit. This causes a scalability bottleneck on
SPECjbb2015 on large systems as there is only one user. Changing to a
per-cpu counter increases throughput of the benchmark by about 30% on a
16-socket, > 1000 thread system.

[rdunlap@infradead.org: fix build errors in kernel/user.c when CONFIG_EPOLL=n]
[npiggin@gmail.com: move ifdefs into wrapper functions, slightly improve panic message]
  Link: https://lkml.kernel.org/r/1628051945.fens3r99ox.astroid@bobo.none
[akpm@linux-foundation.org: tweak user_epoll_alloc(), per Guenter]
  Link: https://lkml.kernel.org/r/20210804191421.GA1900577@roeck-us.net

Link: https://lkml.kernel.org/r/20210802032013.2751916-1-npiggin@gmail.comSigned-off-by: NNicholas Piggin <npiggin@gmail.com>
Reported-by: NAnton Blanchard <anton@ozlabs.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The macros for the unit conversion for frequency are duplicated in
different places.

Provide these macros in the 'units' header, so they can be reused.

Link: https://lkml.kernel.org/r/20210816114732.1834145-3-daniel.lezcano@linaro.orgSigned-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: NChristian Eggers <ceggers@arri.de>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Lukasz Luba <lukasz.luba@arm.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "Add Hz macros", v3.

There are multiple definitions of the HZ_PER_MHZ or HZ_PER_KHZ in the
different drivers.  Instead of duplicating this definition again and
again, add one in the units.h header to be reused in all the place the
redefiniton occurs.

At the same time, change the type of the Watts, as they can not be
negative.

This patch (of 10):

The users of the macros are safe to be assigned with an unsigned instead
of signed as the variables using them are themselves unsigned.

Link: https://lkml.kernel.org/r/20210816114732.1834145-1-daniel.lezcano@linaro.org
Link: https://lkml.kernel.org/r/20210816114732.1834145-2-daniel.lezcano@linaro.orgSigned-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Christian Eggers <ceggers@arri.de>
Cc: Lukasz Luba <lukasz.luba@arm.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix trivia typo Not -> Note in the comment to DO_ONCE().

Link: https://lkml.kernel.org/r/20210722184349.76290-1-andriy.shevchenko@linux.intel.comSigned-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

DAMON is designed to be used by kernel space code such as the memory
management subsystems, and therefore it provides only kernel space API.
That said, letting the user space control DAMON could provide some
benefits to them.  For example, it will allow user space to analyze their
specific workloads and make their own special optimizations.

For such cases, this commit implements a simple DAMON application kernel
module, namely 'damon-dbgfs', which merely wraps the DAMON api and exports
those to the user space via the debugfs.

'damon-dbgfs' exports three files, ``attrs``, ``target_ids``, and
``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.

Attributes
----------

Users can read and write the ``sampling interval``, ``aggregation
interval``, ``regions update interval``, and min/max number of monitoring
target regions by reading from and writing to the ``attrs`` file.  For
example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10,
1000 and check it again::

    # cd <debugfs>/damon
    # echo 5000 100000 1000000 10 1000 > attrs
    # cat attrs
    5000 100000 1000000 10 1000

Target IDs
----------

Some types of address spaces supports multiple monitoring target.  For
example, the virtual memory address spaces monitoring can have multiple
processes as the monitoring targets.  Users can set the targets by writing
relevant id values of the targets to, and get the ids of the current
targets by reading from the ``target_ids`` file.  In case of the virtual
address spaces monitoring, the values should be pids of the monitoring
target processes.  For example, below commands set processes having pids
42 and 4242 as the monitoring targets and check it again::

    # cd <debugfs>/damon
    # echo 42 4242 > target_ids
    # cat target_ids
    42 4242

Note that setting the target ids doesn't start the monitoring.

Turning On/Off
--------------

Setting the files as described above doesn't incur effect unless you
explicitly start the monitoring.  You can start, stop, and check the
current status of the monitoring by writing to and reading from the
``monitor_on`` file.  Writing ``on`` to the file starts the monitoring of
the targets with the attributes.  Writing ``off`` to the file stops those.
DAMON also stops if every targets are invalidated (in case of the virtual
memory monitoring, target processes are invalidated when terminated).
Below example commands turn on, off, and check the status of DAMON::

    # cd <debugfs>/damon
    # echo on > monitor_on
    # echo off > monitor_on
    # cat monitor_on
    off

Please note that you cannot write to the above-mentioned debugfs files
while the monitoring is turned on.  If you write to the files while DAMON
is running, an error code such as ``-EBUSY`` will be returned.

[akpm@linux-foundation.org: remove unneeded "alloc failed" printks]
[akpm@linux-foundation.org: replace macro with static inline]

Link: https://lkml.kernel.org/r/20210716081449.22187-8-sj38.park@gmail.comSigned-off-by: NSeongJae Park <sjpark@amazon.de>
Reviewed-by: NLeonard Foerster <foersleo@amazon.de>
Reviewed-by: NFernand Sieber <sieberf@amazon.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This commit introduces a reference implementation of the address space
specific low level primitives for the virtual address space, so that users
of DAMON can easily monitor the data accesses on virtual address spaces of
specific processes by simply configuring the implementation to be used by
DAMON.

The low level primitives for the fundamental access monitoring are defined
in two parts:

1. Identification of the monitoring target address range for the address
   space.
2. Access check of specific address range in the target space.

The reference implementation for the virtual address space does the works
as below.

PTE Accessed-bit Based Access Check
-----------------------------------

The implementation uses PTE Accessed-bit for basic access checks.  That
is, it clears the bit for the next sampling target page and checks whether
it is set again after one sampling period.  This could disturb the reclaim
logic.  DAMON uses ``PG_idle`` and ``PG_young`` page flags to solve the
conflict, as Idle page tracking does.

VMA-based Target Address Range Construction
-------------------------------------------

Only small parts in the super-huge virtual address space of the processes
are mapped to physical memory and accessed.  Thus, tracking the unmapped
address regions is just wasteful.  However, because DAMON can deal with
some level of noise using the adaptive regions adjustment mechanism,
tracking every mapping is not strictly required but could even incur a
high overhead in some cases.  That said, too huge unmapped areas inside
the monitoring target should be removed to not take the time for the
adaptive mechanism.

For the reason, this implementation converts the complex mappings to three
distinct regions that cover every mapped area of the address space.  Also,
the two gaps between the three regions are the two biggest unmapped areas
in the given address space.  The two biggest unmapped areas would be the
gap between the heap and the uppermost mmap()-ed region, and the gap
between the lowermost mmap()-ed region and the stack in most of the cases.
Because these gaps are exceptionally huge in usual address spaces,
excluding these will be sufficient to make a reasonable trade-off.  Below
shows this in detail::

    <heap>
    <BIG UNMAPPED REGION 1>
    <uppermost mmap()-ed region>
    (small mmap()-ed regions and munmap()-ed regions)
    <lowermost mmap()-ed region>
    <BIG UNMAPPED REGION 2>
    <stack>

[akpm@linux-foundation.org: mm/damon/vaddr.c needs highmem.h for kunmap_atomic()]
[sjpark@amazon.de: remove unnecessary PAGE_EXTENSION setup]
  Link: https://lkml.kernel.org/r/20210806095153.6444-2-sj38.park@gmail.com
[sjpark@amazon.de: safely walk page table]
  Link: https://lkml.kernel.org/r/20210831161800.29419-1-sj38.park@gmail.com

Link: https://lkml.kernel.org/r/20210716081449.22187-6-sj38.park@gmail.comSigned-off-by: NSeongJae Park <sjpark@amazon.de>
Reviewed-by: NLeonard Foerster <foersleo@amazon.de>
Reviewed-by: NFernand Sieber <sieberf@amazon.com>
Acked-by: NShakeel Butt <shakeelb@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

PG_idle and PG_young allow the two PTE Accessed bit users, Idle Page
Tracking and the reclaim logic concurrently work while not interfering
with each other.  That is, when they need to clear the Accessed bit, they
set PG_young to represent the previous state of the bit, respectively.
And when they need to read the bit, if the bit is cleared, they further
read the PG_young to know whether the other has cleared the bit meanwhile
or not.

For yet another user of the PTE Accessed bit, we could add another page
flag, or extend the mechanism to use the flags.  For the DAMON usecase,
however, we don't need to do that just yet.  IDLE_PAGE_TRACKING and DAMON
are mutually exclusive, so there's only ever going to be one user of the
current set of flags.

In this commit, we split out the CONFIG options to allow for the use of
PG_young and PG_idle outside of idle page tracking.

In the next commit, DAMON's reference implementation of the virtual memory
address space monitoring primitives will use it.

[sjpark@amazon.de: set PAGE_EXTENSION for non-64BIT]
  Link: https://lkml.kernel.org/r/20210806095153.6444-1-sj38.park@gmail.com
[akpm@linux-foundation.org: tweak Kconfig text]
[sjpark@amazon.de: hide PAGE_IDLE_FLAG from users]
  Link: https://lkml.kernel.org/r/20210813081238.34705-1-sj38.park@gmail.com

Link: https://lkml.kernel.org/r/20210716081449.22187-5-sj38.park@gmail.comSigned-off-by: NSeongJae Park <sjpark@amazon.de>
Reviewed-by: NShakeel Butt <shakeelb@google.com>
Reviewed-by: NFernand Sieber <sieberf@amazon.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Even somehow the initial monitoring target regions are well constructed to
fulfill the assumption (pages in same region have similar access
frequencies), the data access pattern can be dynamically changed.  This
will result in low monitoring quality.  To keep the assumption as much as
possible, DAMON adaptively merges and splits each region based on their
access frequency.

For each ``aggregation interval``, it compares the access frequencies of
adjacent regions and merges those if the frequency difference is small.
Then, after it reports and clears the aggregated access frequency of each
region, it splits each region into two or three regions if the total
number of regions will not exceed the user-specified maximum number of
regions after the split.

In this way, DAMON provides its best-effort quality and minimal overhead
while keeping the upper-bound overhead that users set.

Link: https://lkml.kernel.org/r/20210716081449.22187-4-sj38.park@gmail.comSigned-off-by: NSeongJae Park <sjpark@amazon.de>
Reviewed-by: NLeonard Foerster <foersleo@amazon.de>
Reviewed-by: NFernand Sieber <sieberf@amazon.com>
Acked-by: NShakeel Butt <shakeelb@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

To avoid the unbounded increase of the overhead, DAMON groups adjacent
pages that are assumed to have the same access frequencies into a
region.  As long as the assumption (pages in a region have the same
access frequencies) is kept, only one page in the region is required to
be checked.  Thus, for each ``sampling interval``,

 1. the 'prepare_access_checks' primitive picks one page in each region,
 2. waits for one ``sampling interval``,
 3. checks whether the page is accessed meanwhile, and
 4. increases the access count of the region if so.

Therefore, the monitoring overhead is controllable by adjusting the
number of regions.  DAMON allows both the underlying primitives and user
callbacks to adjust regions for the trade-off.  In other words, this
commit makes DAMON to use not only time-based sampling but also
space-based sampling.

This scheme, however, cannot preserve the quality of the output if the
assumption is not guaranteed.  Next commit will address this problem.

Link: https://lkml.kernel.org/r/20210716081449.22187-3-sj38.park@gmail.comSigned-off-by: NSeongJae Park <sjpark@amazon.de>
Reviewed-by: NLeonard Foerster <foersleo@amazon.de>
Reviewed-by: NFernand Sieber <sieberf@amazon.com>
Acked-by: NShakeel Butt <shakeelb@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "Introduce Data Access MONitor (DAMON)", v34.

Introduction
============

DAMON is a data access monitoring framework for the Linux kernel.  The
core mechanisms of DAMON called 'region based sampling' and 'adaptive
regions adjustment' (refer to 'mechanisms.rst' in the 11th patch of this
patchset for the detail) make it

- accurate (The monitored information is useful for DRAM level memory
  management.  It might not appropriate for Cache-level accuracy,
  though.),

- light-weight (The monitoring overhead is low enough to be applied
  online while making no impact on the performance of the target
  workloads.), and

- scalable (the upper-bound of the instrumentation overhead is
  controllable regardless of the size of target workloads.).

Using this framework, therefore, several memory management mechanisms such
as reclamation and THP can be optimized to aware real data access
patterns.  Experimental access pattern aware memory management
optimization works that incurring high instrumentation overhead will be
able to have another try.

Though DAMON is for kernel subsystems, it can be easily exposed to the
user space by writing a DAMON-wrapper kernel subsystem.  Then, user space
users who have some special workloads will be able to write personalized
tools or applications for deeper understanding and specialized
optimizations of their systems.

DAMON is also merged in two public Amazon Linux kernel trees that based on
v5.4.y[1] and v5.10.y[2].

[1] https://github.com/amazonlinux/linux/tree/amazon-5.4.y/master/mm/damon
[2] https://github.com/amazonlinux/linux/tree/amazon-5.10.y/master/mm/damon

The userspace tool[1] is available, released under GPLv2, and actively
being maintained.  I am also planning to implement another basic user
interface in perf[2].  Also, the basic test suite for DAMON is available
under GPLv2[3].

[1] https://github.com/awslabs/damo
[2] https://lore.kernel.org/linux-mm/20210107120729.22328-1-sjpark@amazon.com/
[3] https://github.com/awslabs/damon-tests

Long-term Plan
--------------

DAMON is a part of a project called Data Access-aware Operating System
(DAOS).  As the name implies, I want to improve the performance and
efficiency of systems using fine-grained data access patterns.  The
optimizations are for both kernel and user spaces.  I will therefore
modify or create kernel subsystems, export some of those to user space and
implement user space library / tools.  Below shows the layers and
components for the project.

    ---------------------------------------------------------------------------
    Primitives:     PTE Accessed bit, PG_idle, rmap, (Intel CMT), ...
    Framework:      DAMON
    Features:       DAMOS, virtual addr, physical addr, ...
    Applications:   DAMON-debugfs, (DARC), ...
    ^^^^^^^^^^^^^^^^^^^^^^^    KERNEL SPACE    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    Raw Interface:  debugfs, (sysfs), (damonfs), tracepoints, (sys_damon), ...

    vvvvvvvvvvvvvvvvvvvvvvv    USER SPACE      vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    Library:        (libdamon), ...
    Tools:          DAMO, (perf), ...
    ---------------------------------------------------------------------------

The components in parentheses or marked as '...' are not implemented yet
but in the future plan.  IOW, those are the TODO tasks of DAOS project.
For more detail, please refer to the plans:
https://lore.kernel.org/linux-mm/20201202082731.24828-1-sjpark@amazon.com/

Evaluations
===========

We evaluated DAMON's overhead, monitoring quality and usefulness using 24
realistic workloads on my QEMU/KVM based virtual machine running a kernel
that v24 DAMON patchset is applied.

DAMON is lightweight.  It increases system memory usage by 0.39% and slows
target workloads down by 1.16%.

DAMON is accurate and useful for memory management optimizations.  An
experimental DAMON-based operation scheme for THP, namely 'ethp', removes
76.15% of THP memory overheads while preserving 51.25% of THP speedup.
Another experimental DAMON-based 'proactive reclamation' implementation,
'prcl', reduces 93.38% of residential sets and 23.63% of system memory
footprint while incurring only 1.22% runtime overhead in the best case
(parsec3/freqmine).

NOTE that the experimental THP optimization and proactive reclamation are
not for production but only for proof of concepts.

Please refer to the official document[1] or "Documentation/admin-guide/mm:
Add a document for DAMON" patch in this patchset for detailed evaluation
setup and results.

[1] https://damonitor.github.io/doc/html/latest-damon/admin-guide/mm/damon/eval.html

Real-world User Story
=====================

In summary, DAMON has used on production systems and proved its usefulness.

DAMON as a profiler
-------------------

We analyzed characteristics of a large scale production systems of our
customers using DAMON.  The systems utilize 70GB DRAM and 36 CPUs.  From
this, we were able to find interesting things below.

There were obviously different access pattern under idle workload and
active workload.  Under the idle workload, it accessed large memory
regions with low frequency, while the active workload accessed small
memory regions with high freuqnecy.

DAMON found a 7GB memory region that showing obviously high access
frequency under the active workload.  We believe this is the
performance-effective working set and need to be protected.

There was a 4KB memory region that showing highest access frequency under
not only active but also idle workloads.  We think this must be a hottest
code section like thing that should never be paged out.

For this analysis, DAMON used only 0.3-1% of single CPU time.  Because we
used recording-based analysis, it consumed about 3-12 MB of disk space per
20 minutes.  This is only small amount of disk space, but we can further
reduce the disk usage by using non-recording-based DAMON features.  I'd
like to argue that only DAMON can do such detailed analysis (finding 4KB
highest region in 70GB memory) with the light overhead.

DAMON as a system optimization tool
-----------------------------------

We also found below potential performance problems on the systems and made
DAMON-based solutions.

The system doesn't want to make the workload suffer from the page
reclamation and thus it utilizes enough DRAM but no swap device.  However,
we found the system is actively reclaiming file-backed pages, because the
system has intensive file IO.  The file IO turned out to be not
performance critical for the workload, but the customer wanted to ensure
performance critical file-backed pages like code section to not mistakenly
be evicted.

Using direct IO should or `mlock()` would be a straightforward solution,
but modifying the user space code is not easy for the customer.
Alternatively, we could use DAMON-based operation scheme[1].  By using it,
we can ask DAMON to track access frequency of each region and make
'process_madvise(MADV_WILLNEED)[2]' call for regions having specific size
and access frequency for a time interval.

We also found the system is having high number of TLB misses.  We tried
'always' THP enabled policy and it greatly reduced TLB misses, but the
page reclamation also been more frequent due to the THP internal
fragmentation caused memory bloat.  We could try another DAMON-based
operation scheme that applies 'MADV_HUGEPAGE' to memory regions having
>=2MB size and high access frequency, while applying 'MADV_NOHUGEPAGE' to
regions having <2MB size and low access frequency.

We do not own the systems so we only reported the analysis results and
possible optimization solutions to the customers.  The customers satisfied
about the analysis results and promised to try the optimization guides.

[1] https://lore.kernel.org/linux-mm/20201006123931.5847-1-sjpark@amazon.com/
[2] https://lore.kernel.org/linux-api/20200622192900.22757-4-minchan@kernel.org/

Comparison with Idle Page Tracking
==================================

Idle Page Tracking allows users to set and read idleness of pages using a
bitmap file which represents each page with each bit of the file.  One
recommended usage of it is working set size detection.  Users can do that
by

    1. find PFN of each page for workloads in interest,
    2. set all the pages as idle by doing writes to the bitmap file,
    3. wait until the workload accesses its working set, and
    4. read the idleness of the pages again and count pages became not idle.

NOTE: While Idle Page Tracking is for user space users, DAMON is primarily
designed for kernel subsystems though it can easily exposed to the user
space.  Hence, this section only assumes such user space use of DAMON.

For what use cases Idle Page Tracking would be better?
------------------------------------------------------

1. Flexible usecases other than hotness monitoring.

Because Idle Page Tracking allows users to control the primitive (Page
idleness) by themselves, Idle Page Tracking users can do anything they
want.  Meanwhile, DAMON is primarily designed to monitor the hotness of
each memory region.  For this, DAMON asks users to provide sampling
interval and aggregation interval.  For the reason, there could be some
use case that using Idle Page Tracking is simpler.

2. Physical memory monitoring.

Idle Page Tracking receives PFN range as input, so natively supports
physical memory monitoring.

DAMON is designed to be extensible for multiple address spaces and use
cases by implementing and using primitives for the given use case.
Therefore, by theory, DAMON has no limitation in the type of target
address space as long as primitives for the given address space exists.
However, the default primitives introduced by this patchset supports only
virtual address spaces.

Therefore, for physical memory monitoring, you should implement your own
primitives and use it, or simply use Idle Page Tracking.

Nonetheless, RFC patchsets[1] for the physical memory address space
primitives is already available.  It also supports user memory same to
Idle Page Tracking.

[1] https://lore.kernel.org/linux-mm/20200831104730.28970-1-sjpark@amazon.com/

For what use cases DAMON is better?
-----------------------------------

1. Hotness Monitoring.

Idle Page Tracking let users know only if a page frame is accessed or not.
For hotness check, the user should write more code and use more memory.
DAMON do that by itself.

2. Low Monitoring Overhead

DAMON receives user's monitoring request with one step and then provide
the results.  So, roughly speaking, DAMON require only O(1) user/kernel
context switches.

In case of Idle Page Tracking, however, because the interface receives
contiguous page frames, the number of user/kernel context switches
increases as the monitoring target becomes complex and huge.  As a result,
the context switch overhead could be not negligible.

Moreover, DAMON is born to handle with the monitoring overhead.  Because
the core mechanism is pure logical, Idle Page Tracking users might be able
to implement the mechanism on their own, but it would be time consuming
and the user/kernel context switching will still more frequent than that
of DAMON.  Also, the kernel subsystems cannot use the logic in this case.

3. Page granularity working set size detection.

Until v22 of this patchset, this was categorized as the thing Idle Page
Tracking could do better, because DAMON basically maintains additional
metadata for each of the monitoring target regions.  So, in the page
granularity working set size detection use case, DAMON would incur (number
of monitoring target pages * size of metadata) memory overhead.  Size of
the single metadata item is about 54 bytes, so assuming 4KB pages, about
1.3% of monitoring target pages will be additionally used.

All essential metadata for Idle Page Tracking are embedded in 'struct
page' and page table entries.  Therefore, in this use case, only one
counter variable for working set size accounting is required if Idle Page
Tracking is used.

There are more details to consider, but roughly speaking, this is true in
most cases.

However, the situation changed from v23.  Now DAMON supports arbitrary
types of monitoring targets, which don't use the metadata.  Using that,
DAMON can do the working set size detection with no additional space
overhead but less user-kernel context switch.  A first draft for the
implementation of monitoring primitives for this usage is available in a
DAMON development tree[1].  An RFC patchset for it based on this patchset
will also be available soon.

Since v24, the arbitrary type support is dropped from this patchset
because this patchset doesn't introduce real use of the type.  You can
still get it from the DAMON development tree[2], though.

[1] https://github.com/sjp38/linux/tree/damon/pgidle_hack
[2] https://github.com/sjp38/linux/tree/damon/master

4. More future usecases

While Idle Page Tracking has tight coupling with base primitives (PG_Idle
and page table Accessed bits), DAMON is designed to be extensible for many
use cases and address spaces.  If you need some special address type or
want to use special h/w access check primitives, you can write your own
primitives for that and configure DAMON to use those.  Therefore, if your
use case could be changed a lot in future, using DAMON could be better.

Can I use both Idle Page Tracking and DAMON?
--------------------------------------------

Yes, though using them concurrently for overlapping memory regions could
result in interference to each other.  Nevertheless, such use case would
be rare or makes no sense at all.  Even in the case, the noise would bot
be really significant.  So, you can choose whatever you want depending on
the characteristics of your use cases.

More Information
================

We prepared a showcase web site[1] that you can get more information.
There are

- the official documentations[2],
- the heatmap format dynamic access pattern of various realistic workloads for
  heap area[3], mmap()-ed area[4], and stack[5] area,
- the dynamic working set size distribution[6] and chronological working set
  size changes[7], and
- the latest performance test results[8].

[1] https://damonitor.github.io/_index
[2] https://damonitor.github.io/doc/html/latest-damon
[3] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.0.png.html
[4] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
[5] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.2.png.html
[6] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
[7] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html
[8] https://damonitor.github.io/test/result/perf/latest/html/index.html

Baseline and Complete Git Trees
===============================

The patches are based on the latest -mm tree, specifically
v5.14-rc1-mmots-2021-07-15-18-47 of https://github.com/hnaz/linux-mm.  You can
also clone the complete git tree:

    $ git clone git://github.com/sjp38/linux -b damon/patches/v34

The web is also available:
https://github.com/sjp38/linux/releases/tag/damon/patches/v34

Development Trees
-----------------

There are a couple of trees for entire DAMON patchset series and features
for future release.

- For latest release: https://github.com/sjp38/linux/tree/damon/master
- For next release: https://github.com/sjp38/linux/tree/damon/next

Long-term Support Trees
-----------------------

For people who want to test DAMON but using LTS kernels, there are another
couple of trees based on two latest LTS kernels respectively and
containing the 'damon/master' backports.

- For v5.4.y: https://github.com/sjp38/linux/tree/damon/for-v5.4.y
- For v5.10.y: https://github.com/sjp38/linux/tree/damon/for-v5.10.y

Amazon Linux Kernel Trees
-------------------------

DAMON is also merged in two public Amazon Linux kernel trees that based on
v5.4.y[1] and v5.10.y[2].

[1] https://github.com/amazonlinux/linux/tree/amazon-5.4.y/master/mm/damon
[2] https://github.com/amazonlinux/linux/tree/amazon-5.10.y/master/mm/damon

Git Tree for Diff of Patches
============================

For easy review of diff between different versions of each patch, I
prepared a git tree containing all versions of the DAMON patchset series:
https://github.com/sjp38/damon-patches

You can clone it and use 'diff' for easy review of changes between
different versions of the patchset.  For example:

    $ git clone https://github.com/sjp38/damon-patches && cd damon-patches
    $ diff -u damon/v33 damon/v34

Sequence Of Patches
===================

First three patches implement the core logics of DAMON.  The 1st patch
introduces basic sampling based hotness monitoring for arbitrary types of
targets.  Following two patches implement the core mechanisms for control
of overhead and accuracy, namely regions based sampling (patch 2) and
adaptive regions adjustment (patch 3).

Now the essential parts of DAMON is complete, but it cannot work unless
someone provides monitoring primitives for a specific use case.  The
following two patches make it just work for virtual address spaces
monitoring.  The 4th patch makes 'PG_idle' can be used by DAMON and the
5th patch implements the virtual memory address space specific monitoring
primitives using page table Accessed bits and the 'PG_idle' page flag.

Now DAMON just works for virtual address space monitoring via the kernel
space api.  To let the user space users can use DAMON, following four
patches add interfaces for them.  The 6th patch adds a tracepoint for
monitoring results.  The 7th patch implements a DAMON application kernel
module, namely damon-dbgfs, that simply wraps DAMON and exposes DAMON
interface to the user space via the debugfs interface.  The 8th patch
further exports pid of monitoring thread (kdamond) to user space for
easier cpu usage accounting, and the 9th patch makes the debugfs interface
to support multiple contexts.

Three patches for maintainability follows.  The 10th patch adds
documentations for both the user space and the kernel space.  The 11th
patch provides unit tests (based on the kunit) while the 12th patch adds
user space tests (based on the kselftest).

Finally, the last patch (13th) updates the MAINTAINERS file.

This patch (of 13):

DAMON is a data access monitoring framework for the Linux kernel.  The
core mechanisms of DAMON make it

 - accurate (the monitoring output is useful enough for DRAM level
   performance-centric memory management; It might be inappropriate for
   CPU cache levels, though),
 - light-weight (the monitoring overhead is normally low enough to be
   applied online), and
 - scalable (the upper-bound of the overhead is in constant range
   regardless of the size of target workloads).

Using this framework, hence, we can easily write efficient kernel space
data access monitoring applications.  For example, the kernel's memory
management mechanisms can make advanced decisions using this.
Experimental data access aware optimization works that incurring high
access monitoring overhead could again be implemented on top of this.

Due to its simple and flexible interface, providing user space interface
would be also easy.  Then, user space users who have some special
workloads can write personalized applications for better understanding and
optimizations of their workloads and systems.

===

Nevertheless, this commit is defining and implementing only basic access
check part without the overhead-accuracy handling core logic.  The basic
access check is as below.

The output of DAMON says what memory regions are how frequently accessed
for a given duration.  The resolution of the access frequency is
controlled by setting ``sampling interval`` and ``aggregation interval``.
In detail, DAMON checks access to each page per ``sampling interval`` and
aggregates the results.  In other words, counts the number of the accesses
to each region.  After each ``aggregation interval`` passes, DAMON calls
callback functions that previously registered by users so that users can
read the aggregated results and then clears the results.  This can be
described in below simple pseudo-code::

    init()
    while monitoring_on:
        for page in monitoring_target:
            if accessed(page):
                nr_accesses[page] += 1
        if time() % aggregation_interval == 0:
            for callback in user_registered_callbacks:
                callback(monitoring_target, nr_accesses)
            for page in monitoring_target:
                nr_accesses[page] = 0
        if time() % update_interval == 0:
            update()
        sleep(sampling interval)

The target regions constructed at the beginning of the monitoring and
updated after each ``regions_update_interval``, because the target regions
could be dynamically changed (e.g., mmap() or memory hotplug).  The
monitoring overhead of this mechanism will arbitrarily increase as the
size of the target workload grows.

The basic monitoring primitives for actual access check and dynamic target
regions construction aren't in the core part of DAMON.  Instead, it allows
users to implement their own primitives that are optimized for their use
case and configure DAMON to use those.  In other words, users cannot use
current version of DAMON without some additional works.

Following commits will implement the core mechanisms for the
overhead-accuracy control and default primitives implementations.

Link: https://lkml.kernel.org/r/20210716081449.22187-1-sj38.park@gmail.com
Link: https://lkml.kernel.org/r/20210716081449.22187-2-sj38.park@gmail.comSigned-off-by: NSeongJae Park <sjpark@amazon.de>
Reviewed-by: NLeonard Foerster <foersleo@amazon.de>
Reviewed-by: NFernand Sieber <sieberf@amazon.com>
Acked-by: NShakeel Butt <shakeelb@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Marco Elver <elver@google.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Instead of hard-coding ((1UL << NR_PAGEFLAGS) - 1) everywhere, introducing
PAGEFLAGS_MASK to make the code clear to get the page flags.

Link: https://lkml.kernel.org/r/20210819150712.59948-1-songmuchun@bytedance.comSigned-off-by: NMuchun Song <songmuchun@bytedance.com>
Reviewed-by: NRoman Gushchin <guro@fb.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NShakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kmap_atomic() disables preemption and pagefaults for historical reasons.
The conversion to kmap_local(), which only disables migration, cannot be
done wholesale because quite some call sites need to be updated to
accommodate with the changed semantics.

On PREEMPT_RT enabled kernels the kmap_atomic() semantics are problematic
due to the implicit disabling of preemption which makes it impossible to
acquire 'sleeping' spinlocks within the kmap atomic sections.

PREEMPT_RT replaces the preempt_disable() with a migrate_disable() for
more than a decade.  It could be argued that this is a justification to do
this unconditionally, but PREEMPT_RT covers only a limited number of
architectures and it disables some functionality which limits the coverage
further.

Limit the replacement to PREEMPT_RT for now.

Link: https://lkml.kernel.org/r/20210810091116.pocdmaatdcogvdso@linutronix.deSigned-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "small ioremap cleanups".

The first patch moves a little code around the vmalloc/ioremap boundary
following a bigger move by Nick earlier.  The second enforces
non-executable mapping on ioremap just like we do for vmap.  No driver
currently uses executable mappings anyway, as they should.

This patch (of 2):

This keeps it together with the implementation, and to remove the
vmap_range wrapper.

Link: https://lkml.kernel.org/r/20210824091259.1324527-1-hch@lst.de
Link: https://lkml.kernel.org/r/20210824091259.1324527-2-hch@lst.deSigned-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NNicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There is a READ_ONCE() in the macro of compound_head(), which will prevent
compiler from optimizing the code when there are more than once calling of
it in a function.  Remove the redundant calling of compound_head() from
page_to_index() and page_add_file_rmap() for better code generation.

Link: https://lkml.kernel.org/r/20210811101431.83940-1-songmuchun@bytedance.comSigned-off-by: NMuchun Song <songmuchun@bytedance.com>
Reviewed-by: NDavid Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, the "auto-movable" online policy does not allow for hotplugged
KERNEL (ZONE_NORMAL) memory to increase the amount of MOVABLE memory we
can have, primarily, because there is no coordiantion across memory
devices and we don't want to create zone-imbalances accidentially when
unplugging memory.

However, within a single memory device it's different.  Let's allow for
KERNEL memory within a dynamic memory group to allow for more MOVABLE
within the same memory group.  The only thing we have to take care of is
that the managing driver avoids zone imbalances by unplugging MOVABLE
memory first, otherwise there can be corner cases where unplug of memory
could result in (accidential) zone imbalances.

virtio-mem is the only user of dynamic memory groups and recently added
support for prioritizing unplug of ZONE_MOVABLE over ZONE_NORMAL, so we
don't need a new toggle to enable it for dynamic memory groups.

We limit this handling to dynamic memory groups, because:

* We want to keep the runtime overhead for collecting stats when
  onlining a single memory block small.  We tend to have only a handful of
  dynamic memory groups, but we can have quite some static memory groups
  (e.g., 256 DIMMs).

* It doesn't make too much sense for static memory groups, as we try
  onlining all applicable memory blocks either completely to ZONE_MOVABLE
  or not.  In ordinary operation, we won't have a mixture of zones within
  a static memory group.

When adding memory to a dynamic memory group, we'll first online memory to
ZONE_MOVABLE as long as early KERNEL memory allows for it.  Then, we'll
online the next unit(s) to ZONE_NORMAL, until we can online the next
unit(s) to ZONE_MOVABLE.

For a simple virtio-mem device with a MOVABLE:KERNEL ratio of 3:1, it will
result in a layout like:

  [M][M][M][M][M][M][M][M][N][M][M][M][N][M][M][M]...
  ^ movable memory due to early kernel memory
			   ^ allows for more movable memory ...
			      ^-----^ ... here
				       ^ allows for more movable memory ...
				          ^-----^ ... here

While the created layout is sub-optimal when it comes to contiguous zones,
it gives us the maximum flexibility when dynamically growing/shrinking a
device; we can grow small VMs really big in small steps, and still shrink
reliably to e.g., 1/4 of the maximum VM size in this example, removing
full memory blocks along with meta data more reliably.

Mark dynamic memory groups in the xarray such that we can efficiently
iterate over them when collecting stats.  In usual setups, we have one
virtio-mem device per NUMA node, and usually only a small number of NUMA
nodes.

Note: for now, there seems to be no compelling reason to make this
behavior configurable.

Link: https://lkml.kernel.org/r/20210806124715.17090-10-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use memory groups to improve our "auto-movable" onlining policy:

1. For static memory groups (e.g., a DIMM), online a memory block MOVABLE
   only if all other memory blocks in the group are either MOVABLE or could
   be onlined MOVABLE. A DIMM will either be MOVABLE or not, not a mixture.

2. For dynamic memory groups (e.g., a virtio-mem device), online a
   memory block MOVABLE only if all other memory blocks inside the
   current unit are either MOVABLE or could be onlined MOVABLE. For a
   virtio-mem device with a device block size with 512 MiB, all 128 MiB
   memory blocks wihin a 512 MiB unit will either be MOVABLE or not, not
   a mixture.

We have to pass the memory group to zone_for_pfn_range() to take the
memory group into account.

Note: for now, there seems to be no compelling reason to make this
behavior configurable.

Link: https://lkml.kernel.org/r/20210806124715.17090-9-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Let's track all present pages in each memory group.  Especially, track
memory present in ZONE_MOVABLE and memory present in one of the kernel
zones (which really only is ZONE_NORMAL right now as memory groups only
apply to hotplugged memory) separately within a memory group, to prepare
for making smart auto-online decision for individual memory blocks within
a memory group based on group statistics.

Link: https://lkml.kernel.org/r/20210806124715.17090-5-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In our "auto-movable" memory onlining policy, we want to make decisions
across memory blocks of a single memory device.  Examples of memory
devices include ACPI memory devices (in the simplest case a single DIMM)
and virtio-mem.  For now, we don't have a connection between a single
memory block device and the real memory device.  Each memory device
consists of 1..X memory block devices.

Let's logically group memory blocks belonging to the same memory device in
"memory groups".  Memory groups can span multiple physical ranges and a
memory group itself does not contain any information regarding physical
ranges, only properties (e.g., "max_pages") necessary for improved memory
onlining.

Introduce two memory group types:

1) Static memory group: E.g., a single ACPI memory device, consisting
   of 1..X memory resources.  A memory group consists of 1..Y memory
   blocks.  The whole group is added/removed in one go.  If any part
   cannot get offlined, the whole group cannot be removed.

2) Dynamic memory group: E.g., a single virtio-mem device.  Memory is
   dynamically added/removed in a fixed granularity, called a "unit",
   consisting of 1..X memory blocks.  A unit is added/removed in one go.
   If any part of a unit cannot get offlined, the whole unit cannot be
   removed.

In case of 1) we usually want either all memory managed by ZONE_MOVABLE or
none.  In case of 2) we usually want to have as many units as possible
managed by ZONE_MOVABLE.  We want a single unit to be of the same type.

For now, memory groups are an internal concept that is not exposed to user
space; we might want to change that in the future, though.

add_memory() users can specify a mgid instead of a nid when passing the
MHP_NID_IS_MGID flag.

Link: https://lkml.kernel.org/r/20210806124715.17090-4-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "mm/memory_hotplug: "auto-movable" online policy and memory groups", v3.

I. Goal

The goal of this series is improving in-kernel auto-online support.  It
tackles the fundamental problems that:

 1) We can create zone imbalances when onlining all memory blindly to
    ZONE_MOVABLE, in the worst case crashing the system. We have to know
    upfront how much memory we are going to hotplug such that we can
    safely enable auto-onlining of all hotplugged memory to ZONE_MOVABLE
    via "online_movable". This is far from practical and only applicable in
    limited setups -- like inside VMs under the RHV/oVirt hypervisor which
    will never hotplug more than 3 times the boot memory (and the
    limitation is only in place due to the Linux limitation).

 2) We see more setups that implement dynamic VM resizing, hot(un)plugging
    memory to resize VM memory. In these setups, we might hotplug a lot of
    memory, but it might happen in various small steps in both directions
    (e.g., 2 GiB -> 8 GiB -> 4 GiB -> 16 GiB ...). virtio-mem is the
    primary driver of this upstream right now, performing such dynamic
    resizing NUMA-aware via multiple virtio-mem devices.

    Onlining all hotplugged memory to ZONE_NORMAL means we basically have
    no hotunplug guarantees. Onlining all to ZONE_MOVABLE means we can
    easily run into zone imbalances when growing a VM. We want a mixture,
    and we want as much memory as reasonable/configured in ZONE_MOVABLE.
    Details regarding zone imbalances can be found at [1].

 3) Memory devices consist of 1..X memory block devices, however, the
    kernel doesn't really track the relationship. Consequently, also user
    space has no idea. We want to make per-device decisions.

    As one example, for memory hotunplug it doesn't make sense to use a
    mixture of zones within a single DIMM: we want all MOVABLE if
    possible, otherwise all !MOVABLE, because any !MOVABLE part will easily
    block the whole DIMM from getting hotunplugged.

    As another example, virtio-mem operates on individual units that span
    1..X memory blocks. Similar to a DIMM, we want a unit to either be all
    MOVABLE or !MOVABLE. A "unit" can be thought of like a DIMM, however,
    all units of a virtio-mem device logically belong together and are
    managed (added/removed) by a single driver. We want as much memory of
    a virtio-mem device to be MOVABLE as possible.

 4) We want memory onlining to be done right from the kernel while adding
    memory, not triggered by user space via udev rules; for example, this
    is reqired for fast memory hotplug for drivers that add individual
    memory blocks, like virito-mem. We want a way to configure a policy in
    the kernel and avoid implementing advanced policies in user space.

The auto-onlining support we have in the kernel is not sufficient.  All we
have is a) online everything MOVABLE (online_movable) b) online everything
!MOVABLE (online_kernel) c) keep zones contiguous (online).  This series
allows configuring c) to mean instead "online movable if possible
according to the coniguration, driven by a maximum MOVABLE:KERNEL ratio"
-- a new onlining policy.

II. Approach

This series does 3 things:

 1) Introduces the "auto-movable" online policy that initially operates on
    individual memory blocks only. It uses a maximum MOVABLE:KERNEL ratio
    to make a decision whether a memory block will be onlined to
    ZONE_MOVABLE or not. However, in the basic form, hotplugged KERNEL
    memory does not allow for more MOVABLE memory (details in the
    patches). CMA memory is treated like MOVABLE memory.

 2) Introduces static (e.g., DIMM) and dynamic (e.g., virtio-mem) memory
    groups and uses group information to make decisions in the
    "auto-movable" online policy across memory blocks of a single memory
    device (modeled as memory group). More details can be found in patch
    #3 or in the DIMM example below.

 3) Maximizes ZONE_MOVABLE memory within dynamic memory groups, by
    allowing ZONE_NORMAL memory within a dynamic memory group to allow for
    more ZONE_MOVABLE memory within the same memory group. The target use
    case is dynamic VM resizing using virtio-mem. See the virtio-mem
    example below.

I remember that the basic idea of using a ratio to implement a policy in
the kernel was once mentioned by Vitaly Kuznetsov, but I might be wrong (I
lost the pointer to that discussion).

For me, the main use case is using it along with virtio-mem (and DIMMs /
ppc64 dlpar where necessary) for dynamic resizing of VMs, increasing the
amount of memory we can hotunplug reliably again if we might eventually
hotplug a lot of memory to a VM.

III. Target Usage

The target usage will be:

 1) Linux boots with "mhp_default_online_type=offline"

 2) User space (e.g., systemd unit) configures memory onlining (according
    to a config file and system properties), for example:
    * Setting memory_hotplug.online_policy=auto-movable
    * Setting memory_hotplug.auto_movable_ratio=301
    * Setting memory_hotplug.auto_movable_numa_aware=true

 3) User space enabled auto onlining via "echo online >
    /sys/devices/system/memory/auto_online_blocks"

 4) User space triggers manual onlining of all already-offline memory
    blocks (go over offline memory blocks and set them to "online")

IV. Example

For DIMMs, hotplugging 4 GiB DIMMs to a 4 GiB VM with a configured ratio of
301% results in the following layout:
	Memory block 0-15:    DMA32   (early)
	Memory block 32-47:   Normal  (early)
	Memory block 48-79:   Movable (DIMM 0)
	Memory block 80-111:  Movable (DIMM 1)
	Memory block 112-143: Movable (DIMM 2)
	Memory block 144-275: Normal  (DIMM 3)
	Memory block 176-207: Normal  (DIMM 4)
	... all Normal
	(-> hotplugged Normal memory does not allow for more Movable memory)

For virtio-mem, using a simple, single virtio-mem device with a 4 GiB VM
will result in the following layout:
	Memory block 0-15:    DMA32   (early)
	Memory block 32-47:   Normal  (early)
	Memory block 48-143:  Movable (virtio-mem, first 12 GiB)
	Memory block 144:     Normal  (virtio-mem, next 128 MiB)
	Memory block 145-147: Movable (virtio-mem, next 384 MiB)
	Memory block 148:     Normal  (virtio-mem, next 128 MiB)
	Memory block 149-151: Movable (virtio-mem, next 384 MiB)
	... Normal/Movable mixture as above
	(-> hotplugged Normal memory allows for more Movable memory within
	    the same device)

Which gives us maximum flexibility when dynamically growing/shrinking a
VM in smaller steps.

V. Doc Update

I'll update the memory-hotplug.rst documentation, once the overhaul [1] is
usptream. Until then, details can be found in patch #2.

VI. Future Work

 1) Use memory groups for ppc64 dlpar
 2) Being able to specify a portion of (early) kernel memory that will be
    excluded from the ratio. Like "128 MiB globally/per node" are excluded.

    This might be helpful when starting VMs with extremely small memory
    footprint (e.g., 128 MiB) and hotplugging memory later -- not wanting
    the first hotplugged units getting onlined to ZONE_MOVABLE. One
    alternative would be a trigger to not consider ZONE_DMA memory
    in the ratio. We'll have to see if this is really rrequired.
 3) Indicate to user space that MOVABLE might be a bad idea -- especially
    relevant when memory ballooning without support for balloon compaction
    is active.

This patch (of 9):

For implementing a new memory onlining policy, which determines when to
online memory blocks to ZONE_MOVABLE semi-automatically, we need the
number of present early (boot) pages -- present pages excluding hotplugged
pages.  Let's track these pages per zone.

Pass a page instead of the zone to adjust_present_page_count(), similar as
adjust_managed_page_count() and derive the zone from the page.

It's worth noting that a memory block to be offlined/onlined is either
completely "early" or "not early".  add_memory() and friends can only add
complete memory blocks and we only online/offline complete (individual)
memory blocks.

Link: https://lkml.kernel.org/r/20210806124715.17090-1-david@redhat.com
Link: https://lkml.kernel.org/r/20210806124715.17090-2-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There is only a single user remaining.  We can simply lookup the nid only
used for node offlining purposes when walking our memory blocks.  We don't
expect to remove multi-nid ranges; and if we'd ever do, we most probably
don't care about removing multi-nid ranges that actually result in empty
nodes.

If ever required, we can detect the "multi-nid" scenario and simply try
offlining all online nodes.

Link: https://lkml.kernel.org/r/20210712124052.26491-4-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Scott Cheloha <cheloha@linux.ibm.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jia He <justin.he@arm.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta@ionos.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Sergei Trofimovich <slyfox@gentoo.org>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The parameter is unused, let's remove it.

Link: https://lkml.kernel.org/r/20210712124052.26491-3-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> [powerpc]
Acked-by: Heiko Carstens <hca@linux.ibm.com>	[s390]
Reviewed-by: NPankaj Gupta <pankaj.gupta@ionos.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Sergei Trofimovich <slyfox@gentoo.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Joe Perches <joe@perches.com>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Jia He <justin.he@arm.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Scott Cheloha <cheloha@linux.ibm.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "mm/memory_hotplug: preparatory patches for new online policy and memory"

These are all cleanups and one fix previously sent as part of [1]:
[PATCH v1 00/12] mm/memory_hotplug: "auto-movable" online policy and memory
groups.

These patches make sense even without the other series, therefore I pulled
them out to make the other series easier to digest.

[1] https://lkml.kernel.org/r/20210607195430.48228-1-david@redhat.com

This patch (of 4):

Checkpatch complained on a follow-up patch that we are using "unsigned"
here, which defaults to "unsigned int" and checkpatch is correct.

As we will search for a fitting zone using the wrong pfn, we might end
up onlining memory to one of the special kernel zones, such as ZONE_DMA,
which can end badly as the onlined memory does not satisfy properties of
these zones.

Use "unsigned long" instead, just as we do in other places when handling
PFNs.  This can bite us once we have physical addresses in the range of
multiple TB.

Link: https://lkml.kernel.org/r/20210712124052.26491-2-david@redhat.com
Fixes: e5e68930 ("mm, memory_hotplug: display allowed zones in the preferred ordering")
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NPankaj Gupta <pankaj.gupta@ionos.com>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: virtualization@lists.linux-foundation.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jia He <justin.he@arm.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Scott Cheloha <cheloha@linux.ibm.com>
Cc: Sergei Trofimovich <slyfox@gentoo.org>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE".

After recent updates to freeing unused parts of the memory map, no
architecture can have holes in the memory map within a pageblock.  This
makes pfn_valid_within() check and CONFIG_HOLES_IN_ZONE configuration
option redundant.

The first patch removes them both in a mechanical way and the second patch
simplifies memory_hotplug::test_pages_in_a_zone() that had
pfn_valid_within() surrounded by more logic than simple if.

This patch (of 2):

After recent changes in freeing of the unused parts of the memory map and
rework of pfn_valid() in arm and arm64 there are no architectures that can
have holes in the memory map within a pageblock and so nothing can enable
CONFIG_HOLES_IN_ZONE which guards non trivial implementation of
pfn_valid_within().

With that, pfn_valid_within() is always hardwired to 1 and can be
completely removed.

Remove calls to pfn_valid_within() and CONFIG_HOLES_IN_ZONE.

Link: https://lkml.kernel.org/r/20210713080035.7464-1-rppt@kernel.org
Link: https://lkml.kernel.org/r/20210713080035.7464-2-rppt@kernel.orgSigned-off-by: NMike Rapoport <rppt@linux.ibm.com>
Acked-by: NDavid Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

timespec64_ns() prevents multiplication overflows by comparing the seconds
value of the timespec to KTIME_SEC_MAX. If the value is greater or equal it
returns KTIME_MAX.

But that check casts the signed seconds value to unsigned which makes the
comparision true for all negative values and therefore return wrongly
KTIME_MAX.

Negative second values are perfectly valid and required in some places,
e.g. ptp_clock_adjtime().

Remove the cast and add a check for the negative boundary which is required
to prevent undefined behaviour due to multiplication underflow.

Fixes: cb477557 ("time: Prevent undefined behaviour in timespec64_to_ns()")'
Signed-off-by: NLukas Hannen <lukas.hannen@opensource.tttech-industrial.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/AM6PR01MB541637BD6F336B8FFB72AF80EEC69@AM6PR01MB5416.eurprd01.prod.exchangelabs.com

Fix the kernel-doc comments for the improved Energy Model documentation.
Signed-off-by: NLukasz Luba <lukasz.luba@arm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This reverts commit 9857a17f.

That commit was completely broken, and I should have caught on to it
earlier.  But happily, the kernel test robot noticed the breakage fairly
quickly.

The breakage is because "try_get_page()" is about avoiding the page
reference count overflow case, but is otherwise the exact same as a
plain "get_page()".

In contrast, "try_get_compound_head()" is an entirely different beast,
and uses __page_cache_add_speculative() because it's not just about the
page reference count, but also about possibly racing with the underlying
page going away.

So all the commentary about how

 "try_get_page() has fallen a little behind in terms of maintenance,
  try_get_compound_head() handles speculative page references more
  thoroughly"

was just completely wrong: yes, try_get_compound_head() handles
speculative page references, but the point is that try_get_page() does
not, and must not.

So there's no lack of maintainance - there are fundamentally different
semantics.

A speculative page reference would be entirely wrong in "get_page()",
and it's entirely wrong in "try_get_page()".  It's not about
speculation, it's purely about "uhhuh, you can't get this page because
you've tried to increment the reference count too much already".

The reason the kernel test robot noticed this bug was that it hit the
VM_BUG_ON() in __page_cache_add_speculative(), which is all about
verifying that the context of any speculative page access is correct.
But since that isn't what try_get_page() is all about, the VM_BUG_ON()
tests things that are not correct to test for try_get_page().
Reported-by: Nkernel test robot <oliver.sang@intel.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Joakim Zhang reports that Wake-on-Lan with the stmmac ethernet driver broke
when moving the incorrect handling of mac link state out of mac_config().
This reason this breaks is because the stmmac's WoL is handled by the MAC
rather than the PHY, and phylink doesn't cater for that scenario.

This patch adds the necessary phylink code to handle suspend/resume events
according to whether the MAC still needs a valid link or not. This is the
barest minimum for this support.
Reported-by: NJoakim Zhang <qiangqing.zhang@nxp.com>
Tested-by: NJoakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: NRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: NJoakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch introduces an attribute for vDPA device to indicate
whether virtual address can be used. If vDPA device driver set
it, vhost-vdpa bus driver will not pin user page and transfer
userspace virtual address instead of physical address during
DMA mapping. And corresponding vma->vm_file and offset will be
also passed as an opaque pointer.
Suggested-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NXie Yongji <xieyongji@bytedance.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210831103634.33-11-xieyongji@bytedance.comSigned-off-by: NMichael S. Tsirkin <mst@redhat.com>