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  1. 14 8月, 2013 1 次提交
  3. 21 6月, 2012 1 次提交
    • A
      thp: avoid atomic64_read in pmd_read_atomic for 32bit PAE · e4eed03f
      由 Andrea Arcangeli 提交于 
      In the x86 32bit PAE CONFIG_TRANSPARENT_HUGEPAGE=y case while holding the
mmap_sem for reading, cmpxchg8b cannot be used to read pmd contents under
Xen.

So instead of dealing only with "consistent" pmdvals in
pmd_none_or_trans_huge_or_clear_bad() (which would be conceptually
simpler) we let pmd_none_or_trans_huge_or_clear_bad() deal with pmdvals
where the low 32bit and high 32bit could be inconsistent (to avoid having
to use cmpxchg8b).

The only guarantee we get from pmd_read_atomic is that if the low part of
the pmd was found null, the high part will be null too (so the pmd will be
considered unstable).  And if the low part of the pmd is found "stable"
later, then it means the whole pmd was read atomically (because after a
pmd is stable, neither MADV_DONTNEED nor page faults can alter it anymore,
and we read the high part after the low part).

In the 32bit PAE x86 case, it is enough to read the low part of the pmdval
atomically to declare the pmd as "stable" and that's true for THP and no
THP, furthermore in the THP case we also have a barrier() that will
prevent any inconsistent pmdvals to be cached by a later re-read of the
*pmd.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: Jonathan Nieder <jrnieder@gmail.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Tested-by: NAndrew Jones <drjones@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e4eed03f
  5. 06 6月, 2012 1 次提交
  7. 30 5月, 2012 1 次提交
    • A
      mm: pmd_read_atomic: fix 32bit PAE pmd walk vs pmd_populate SMP race condition · 26c19178
      由 Andrea Arcangeli 提交于 
      When holding the mmap_sem for reading, pmd_offset_map_lock should only
run on a pmd_t that has been read atomically from the pmdp pointer,
otherwise we may read only half of it leading to this crash.

PID: 11679  TASK: f06e8000  CPU: 3   COMMAND: "do_race_2_panic"
 #0 [f06a9dd8] crash_kexec at c049b5ec
 #1 [f06a9e2c] oops_end at c083d1c2
 #2 [f06a9e40] no_context at c0433ded
 #3 [f06a9e64] bad_area_nosemaphore at c043401a
 #4 [f06a9e6c] __do_page_fault at c0434493
 #5 [f06a9eec] do_page_fault at c083eb45
 #6 [f06a9f04] error_code (via page_fault) at c083c5d5
    EAX: 01fb470c EBX: fff35000 ECX: 00000003 EDX: 00000100 EBP:
    00000000
    DS:  007b     ESI: 9e201000 ES:  007b     EDI: 01fb4700 GS:  00e0
    CS:  0060     EIP: c083bc14 ERR: ffffffff EFLAGS: 00010246
 #7 [f06a9f38] _spin_lock at c083bc14
 #8 [f06a9f44] sys_mincore at c0507b7d
 #9 [f06a9fb0] system_call at c083becd
                         start           len
    EAX: ffffffda  EBX: 9e200000  ECX: 00001000  EDX: 6228537f
    DS:  007b      ESI: 00000000  ES:  007b      EDI: 003d0f00
    SS:  007b      ESP: 62285354  EBP: 62285388  GS:  0033
    CS:  0073      EIP: 00291416  ERR: 000000da  EFLAGS: 00000286

This should be a longstanding bug affecting x86 32bit PAE without THP.
Only archs with 64bit large pmd_t and 32bit unsigned long should be
affected.

With THP enabled the barrier() in pmd_none_or_trans_huge_or_clear_bad()
would partly hide the bug when the pmd transition from none to stable,
by forcing a re-read of the *pmd in pmd_offset_map_lock, but when THP is
enabled a new set of problem arises by the fact could then transition
freely in any of the none, pmd_trans_huge or pmd_trans_stable states.
So making the barrier in pmd_none_or_trans_huge_or_clear_bad()
unconditional isn't good idea and it would be a flakey solution.

This should be fully fixed by introducing a pmd_read_atomic that reads
the pmd in order with THP disabled, or by reading the pmd atomically
with cmpxchg8b with THP enabled.

Luckily this new race condition only triggers in the places that must
already be covered by pmd_none_or_trans_huge_or_clear_bad() so the fix
is localized there but this bug is not related to THP.

NOTE: this can trigger on x86 32bit systems with PAE enabled with more
than 4G of ram, otherwise the high part of the pmd will never risk to be
truncated because it would be zero at all times, in turn so hiding the
SMP race.

This bug was discovered and fully debugged by Ulrich, quote:

----
[..]
pmd_none_or_trans_huge_or_clear_bad() loads the content of edx and
eax.

    496 static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t
    *pmd)
    497 {
    498         /* depend on compiler for an atomic pmd read */
    499         pmd_t pmdval = *pmd;

                                // edi = pmd pointer
0xc0507a74 <sys_mincore+548>:   mov    0x8(%esp),%edi
...
                                // edx = PTE page table high address
0xc0507a84 <sys_mincore+564>:   mov    0x4(%edi),%edx
...
                                // eax = PTE page table low address
0xc0507a8e <sys_mincore+574>:   mov    (%edi),%eax

[..]

Please note that the PMD is not read atomically. These are two "mov"
instructions where the high order bits of the PMD entry are fetched
first. Hence, the above machine code is prone to the following race.

-  The PMD entry {high|low} is 0x0000000000000000.
   The "mov" at 0xc0507a84 loads 0x00000000 into edx.

-  A page fault (on another CPU) sneaks in between the two "mov"
   instructions and instantiates the PMD.

-  The PMD entry {high|low} is now 0x00000003fda38067.
   The "mov" at 0xc0507a8e loads 0xfda38067 into eax.
----
Reported-by: NUlrich Obergfell <uobergfe@redhat.com>
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      26c19178
  9. 18 3月, 2011 1 次提交
    • S
      x86: Flush TLB if PGD entry is changed in i386 PAE mode · 4981d01e
      由 Shaohua Li 提交于 
      According to intel CPU manual, every time PGD entry is changed in i386 PAE
mode, we need do a full TLB flush. Current code follows this and there is
comment for this too in the code.

But current code misses the multi-threaded case. A changed page table
might be used by several CPUs, every such CPU should flush TLB. Usually
this isn't a problem, because we prepopulate all PGD entries at process
fork. But when the process does munmap and follows new mmap, this issue
will be triggered.

When it happens, some CPUs keep doing page faults:

  http://marc.info/?l=linux-kernel&m=129915020508238&w=2

Reported-by: Yasunori Goto<y-goto@jp.fujitsu.com>
Tested-by: Yasunori Goto<y-goto@jp.fujitsu.com>
Reviewed-by: NRik van Riel <riel@redhat.com>
Signed-off-by: Shaohua Li<shaohua.li@intel.com>
Cc: Mallick Asit K <asit.k.mallick@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm <linux-mm@kvack.org>
Cc: stable <stable@kernel.org>
LKML-Reference: <1300246649.2337.95.camel@sli10-conroe>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      4981d01e
  11. 14 1月, 2011 1 次提交
  13. 19 3月, 2009 1 次提交
  15. 07 2月, 2009 8 次提交
  17. 17 12月, 2008 1 次提交
    • J
      x86: consolidate __swp_XXX() macros · 1796316a
      由 Jan Beulich 提交于 
      Impact: cleanup, code robustization

The __swp_...() macros silently relied upon which bits are used for
_PAGE_FILE and _PAGE_PROTNONE. After having changed _PAGE_PROTNONE in
our Xen kernel to no longer overlap _PAGE_PAT, live locks and crashes
were reported that could have been avoided if these macros properly
used the symbolic constants. Since, as pointed out earlier, for Xen
Dom0 support mainline likewise will need to eliminate the conflict
between _PAGE_PAT and _PAGE_PROTNONE, this patch does all the necessary
adjustments, plus it introduces a mechanism to check consistency
between MAX_SWAPFILES_SHIFT and the actual encoding macros.

This also fixes a latent bug in that x86-64 used a 6-bit mask in
__swp_type(), and if MAX_SWAPFILES_SHIFT was increased beyond 5 in (the
seemingly unrelated) linux/swap.h, this would have resulted in a
collision with _PAGE_FILE.

Non-PAE 32-bit code gets similarly adjusted for its pte_to_pgoff() and
pgoff_to_pte() calculations.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      1796316a
  19. 30 10月, 2008 1 次提交
  21. 23 10月, 2008 2 次提交
  23. 10 9月, 2008 1 次提交
    • H
      x86: unsigned long pte_pfn · 91030ca1
      由 Hugh Dickins 提交于 
      pte_pfn() has always been of type unsigned long, even on 32-bit PAE;
but in the current tip/next/mm tree it works out to be unsigned long
long on 64-bit, which gives an irritating warning if you try to printk
a pfn with the usual %lx.

Now use the same pte_pfn() function, moved from pgtable-3level.h
to pgtable.h, for all models: as suggested by Jeremy Fitzhardinge.
And pte_page() can well move along with it (remaining a macro to
avoid dependence on mm_types.h).
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Acked-by: NJeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      91030ca1
  25. 23 7月, 2008 1 次提交
    • V
      x86: consolidate header guards · 77ef50a5
      由 Vegard Nossum 提交于 
      This patch is the result of an automatic script that consolidates the
format of all the headers in include/asm-x86/.

The format:

1. No leading underscore. Names with leading underscores are reserved.
2. Pathname components are separated by two underscores. So we can
   distinguish between mm_types.h and mm/types.h.
3. Everything except letters and numbers are turned into single
   underscores.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>
      77ef50a5
  27. 22 7月, 2008 1 次提交
    • J
      x86: rename PTE_MASK to PTE_PFN_MASK · 59438c9f
      由 Jeremy Fitzhardinge 提交于 
      Rusty, in his peevish way, complained that macros defining constants
should have a name which somewhat accurately reflects the actual
purpose of the constant.

Aside from the fact that PTE_MASK gives no clue as to what's actually
being masked, and is misleadingly similar to the functionally entirely
different PMD_MASK, PUD_MASK and PGD_MASK, I don't really see what the
problem is.

But if this patch silences the incessent noise, then it will have
achieved its goal (TODO: write test-case).
Signed-off-by: NJeremy Fitzhardinge <jeremy@goop.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      59438c9f
  29. 20 5月, 2008 1 次提交
  31. 17 4月, 2008 1 次提交
  33. 04 2月, 2008 3 次提交
  35. 30 1月, 2008 9 次提交
  37. 11 10月, 2007 1 次提交
  39. 17 7月, 2007 1 次提交
  41. 03 5月, 2007 2 次提交