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  1. 31 1月, 2009 1 次提交
  3. 18 1月, 2009 1 次提交
  5. 16 1月, 2009 1 次提交
    • I
      percpu: add optimized generic percpu accessors · 6dbde353
      由 Ingo Molnar 提交于 
      It is an optimization and a cleanup, and adds the following new
generic percpu methods:

  percpu_read()
  percpu_write()
  percpu_add()
  percpu_sub()
  percpu_and()
  percpu_or()
  percpu_xor()

and implements support for them on x86. (other architectures will fall
back to a default implementation)

The advantage is that for example to read a local percpu variable,
instead of this sequence:

 return __get_cpu_var(var);

 ffffffff8102ca2b:	48 8b 14 fd 80 09 74 	mov    -0x7e8bf680(,%rdi,8),%rdx
 ffffffff8102ca32:	81
 ffffffff8102ca33:	48 c7 c0 d8 59 00 00 	mov    $0x59d8,%rax
 ffffffff8102ca3a:	48 8b 04 10          	mov    (%rax,%rdx,1),%rax

We can get a single instruction by using the optimized variants:

 return percpu_read(var);

 ffffffff8102ca3f:	65 48 8b 05 91 8f fd 	mov    %gs:0x7efd8f91(%rip),%rax

I also cleaned up the x86-specific APIs and made the x86 code use
these new generic percpu primitives.

tj: * fixed generic percpu_sub() definition as Roel Kluin pointed out
    * added percpu_and() for completeness's sake
    * made generic percpu ops atomic against preemption
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NTejun Heo <tj@kernel.org>
      6dbde353
  7. 17 12月, 2008 2 次提交
  9. 23 11月, 2008 1 次提交
    • I
      xen: pin correct PGD on suspend · 86bbc2c2
      由 Ian Campbell 提交于 
      Impact: fix Xen guest boot failure

commit eefb47f6 ("xen: use
spin_lock_nest_lock when pinning a pagetable") changed xen_pgd_walk to
walk over mm->pgd rather than taking pgd as an argument.

This breaks xen_mm_(un)pin_all() because it makes init_mm.pgd readonly
instead of the pgd we are interested in and therefore the pin subsequently
fails.

(XEN) mm.c:2280:d15 Bad type (saw 00000000e8000001 != exp 0000000060000000) for mfn bc464 (pfn 21ca7)
(XEN) mm.c:2665:d15 Error while pinning mfn bc464

[   14.586913] 1 multicall(s) failed: cpu 0
[   14.586926] Pid: 14, comm: kstop/0 Not tainted 2.6.28-rc5-x86_32p-xenU-00172-gee2f6cc7 #200
[   14.586940] Call Trace:
[   14.586955]  [<c030c17a>] ? printk+0x18/0x1e
[   14.586972]  [<c0103df3>] xen_mc_flush+0x163/0x1d0
[   14.586986]  [<c0104bc1>] __xen_pgd_pin+0xa1/0x110
[   14.587000]  [<c015a330>] ? stop_cpu+0x0/0xf0
[   14.587015]  [<c0104d7b>] xen_mm_pin_all+0x4b/0x70
[   14.587029]  [<c022bcb9>] xen_suspend+0x39/0xe0
[   14.587042]  [<c015a330>] ? stop_cpu+0x0/0xf0
[   14.587054]  [<c015a3cd>] stop_cpu+0x9d/0xf0
[   14.587067]  [<c01417cd>] run_workqueue+0x8d/0x150
[   14.587080]  [<c030e4b3>] ? _spin_unlock_irqrestore+0x23/0x40
[   14.587094]  [<c014558a>] ? prepare_to_wait+0x3a/0x70
[   14.587107]  [<c0141918>] worker_thread+0x88/0xf0
[   14.587120]  [<c01453c0>] ? autoremove_wake_function+0x0/0x50
[   14.587133]  [<c0141890>] ? worker_thread+0x0/0xf0
[   14.587146]  [<c014509c>] kthread+0x3c/0x70
[   14.587157]  [<c0145060>] ? kthread+0x0/0x70
[   14.587170]  [<c0109d1b>] kernel_thread_helper+0x7/0x10
[   14.587181]   call  1/3: op=14 arg=[c0415000] result=0
[   14.587192]   call  2/3: op=14 arg=[e1ca2000] result=0
[   14.587204]   call  3/3: op=26 arg=[c1808860] result=-22
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Acked-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      86bbc2c2
  11. 07 11月, 2008 2 次提交
    • J
      xen: make sure stray alias mappings are gone before pinning · d05fdf31
      由 Jeremy Fitzhardinge 提交于 
      Xen requires that all mappings of pagetable pages are read-only, so
that they can't be updated illegally.  As a result, if a page is being
turned into a pagetable page, we need to make sure all its mappings
are RO.

If the page had been used for ioremap or vmalloc, it may still have
left over mappings as a result of not having been lazily unmapped.
This change makes sure we explicitly mop them all up before pinning
the page.

Unlike aliases created by kmap, the there can be vmalloc aliases even
for non-high pages, so we must do the flush unconditionally.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d05fdf31
    • J
      x86, xen: fix use of pgd_page now that it really does return a page · 47cb2ed9
      由 Jeremy Fitzhardinge 提交于 
      Impact: fix 32-bit Xen guest boot crash

On 32-bit PAE, pud_page, for no good reason, didn't really return a
struct page *.  Since Jan Beulich's fix "i386/PAE: fix pud_page()",
pud_page does return a struct page *.

Because PAE has 3 pagetable levels, the pud level is folded into the
pgd level, so pgd_page() is the same as pud_page(), and now returns
a struct page *.  Update the xen/mmu.c code which uses pgd_page()
accordingly.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      47cb2ed9
  13. 27 10月, 2008 1 次提交
    • C
      xen: fix Xen domU boot with batched mprotect · 9f32d21c
      由 Chris Lalancette 提交于 
      Impact: fix guest kernel boot crash on certain configs

Recent i686 2.6.27 kernels with a certain amount of memory (between
736 and 855MB) have a problem booting under a hypervisor that supports
batched mprotect (this includes the RHEL-5 Xen hypervisor as well as
any 3.3 or later Xen hypervisor).

The problem ends up being that xen_ptep_modify_prot_commit() is using
virt_to_machine to calculate which pfn to update.  However, this only
works for pages that are in the p2m list, and the pages coming from
change_pte_range() in mm/mprotect.c are kmap_atomic pages.  Because of
this, we can run into the situation where the lookup in the p2m table
returns an INVALID_MFN, which we then try to pass to the hypervisor,
which then (correctly) denies the request to a totally bogus pfn.

The right thing to do is to use arbitrary_virt_to_machine, so that we
can be sure we are modifying the right pfn.  This unfortunately
introduces a performance penalty because of a full page-table-walk,
but we can avoid that penalty for pages in the p2m list by checking if
virt_addr_valid is true, and if so, just doing the lookup in the p2m
table.

The attached patch implements this, and allows my 2.6.27 i686 based
guest with 768MB of memory to boot on a RHEL-5 hypervisor again.
Thanks to Jeremy for the suggestions about how to fix this particular
issue.
Signed-off-by: NChris Lalancette <clalance@redhat.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Chris Lalancette <clalance@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9f32d21c
  15. 20 10月, 2008 1 次提交
    • N
      mm: rewrite vmap layer · db64fe02
      由 Nick Piggin 提交于 
      Rewrite the vmap allocator to use rbtrees and lazy tlb flushing, and
provide a fast, scalable percpu frontend for small vmaps (requires a
slightly different API, though).

The biggest problem with vmap is actually vunmap.  Presently this requires
a global kernel TLB flush, which on most architectures is a broadcast IPI
to all CPUs to flush the cache.  This is all done under a global lock.  As
the number of CPUs increases, so will the number of vunmaps a scaled
workload will want to perform, and so will the cost of a global TLB flush.
 This gives terrible quadratic scalability characteristics.

Another problem is that the entire vmap subsystem works under a single
lock.  It is a rwlock, but it is actually taken for write in all the fast
paths, and the read locking would likely never be run concurrently anyway,
so it's just pointless.

This is a rewrite of vmap subsystem to solve those problems.  The existing
vmalloc API is implemented on top of the rewritten subsystem.

The TLB flushing problem is solved by using lazy TLB unmapping.  vmap
addresses do not have to be flushed immediately when they are vunmapped,
because the kernel will not reuse them again (would be a use-after-free)
until they are reallocated.  So the addresses aren't allocated again until
a subsequent TLB flush.  A single TLB flush then can flush multiple
vunmaps from each CPU.

XEN and PAT and such do not like deferred TLB flushing because they can't
always handle multiple aliasing virtual addresses to a physical address.
They now call vm_unmap_aliases() in order to flush any deferred mappings.
That call is very expensive (well, actually not a lot more expensive than
a single vunmap under the old scheme), however it should be OK if not
called too often.

The virtual memory extent information is stored in an rbtree rather than a
linked list to improve the algorithmic scalability.

There is a per-CPU allocator for small vmaps, which amortizes or avoids
global locking.

To use the per-CPU interface, the vm_map_ram / vm_unmap_ram interfaces
must be used in place of vmap and vunmap.  Vmalloc does not use these
interfaces at the moment, so it will not be quite so scalable (although it
will use lazy TLB flushing).

As a quick test of performance, I ran a test that loops in the kernel,
linearly mapping then touching then unmapping 4 pages.  Different numbers
of tests were run in parallel on an 4 core, 2 socket opteron.  Results are
in nanoseconds per map+touch+unmap.

threads           vanilla         vmap rewrite
1                 14700           2900
2                 33600           3000
4                 49500           2800
8                 70631           2900

So with a 8 cores, the rewritten version is already 25x faster.

In a slightly more realistic test (although with an older and less
scalable version of the patch), I ripped the not-very-good vunmap batching
code out of XFS, and implemented the large buffer mapping with vm_map_ram
and vm_unmap_ram...  along with a couple of other tricks, I was able to
speed up a large directory workload by 20x on a 64 CPU system.  I believe
vmap/vunmap is actually sped up a lot more than 20x on such a system, but
I'm running into other locks now.  vmap is pretty well blown off the
profiles.

Before:
1352059 total                                      0.1401
798784 _write_lock                              8320.6667 <- vmlist_lock
529313 default_idle                             1181.5022
 15242 smp_call_function                         15.8771  <- vmap tlb flushing
  2472 __get_vm_area_node                         1.9312  <- vmap
  1762 remove_vm_area                             4.5885  <- vunmap
   316 map_vm_area                                0.2297  <- vmap
   312 kfree                                      0.1950
   300 _spin_lock                                 3.1250
   252 sn_send_IPI_phys                           0.4375  <- tlb flushing
   238 vmap                                       0.8264  <- vmap
   216 find_lock_page                             0.5192
   196 find_next_bit                              0.3603
   136 sn2_send_IPI                               0.2024
   130 pio_phys_write_mmr                         2.0312
   118 unmap_kernel_range                         0.1229

After:
 78406 total                                      0.0081
 40053 default_idle                              89.4040
 33576 ia64_spinlock_contention                 349.7500
  1650 _spin_lock                                17.1875
   319 __reg_op                                   0.5538
   281 _atomic_dec_and_lock                       1.0977
   153 mutex_unlock                               1.5938
   123 iget_locked                                0.1671
   117 xfs_dir_lookup                             0.1662
   117 dput                                       0.1406
   114 xfs_iget_core                              0.0268
    92 xfs_da_hashname                            0.1917
    75 d_alloc                                    0.0670
    68 vmap_page_range                            0.0462 <- vmap
    58 kmem_cache_alloc                           0.0604
    57 memset                                     0.0540
    52 rb_next                                    0.1625
    50 __copy_user                                0.0208
    49 bitmap_find_free_region                    0.2188 <- vmap
    46 ia64_sn_udelay                             0.1106
    45 find_inode_fast                            0.1406
    42 memcmp                                     0.2188
    42 finish_task_switch                         0.1094
    42 __d_lookup                                 0.0410
    40 radix_tree_lookup_slot                     0.1250
    37 _spin_unlock_irqrestore                    0.3854
    36 xfs_bmapi                                  0.0050
    36 kmem_cache_free                            0.0256
    35 xfs_vn_getattr                             0.0322
    34 radix_tree_lookup                          0.1062
    33 __link_path_walk                           0.0035
    31 xfs_da_do_buf                              0.0091
    30 _xfs_buf_find                              0.0204
    28 find_get_page                              0.0875
    27 xfs_iread                                  0.0241
    27 __strncpy_from_user                        0.2812
    26 _xfs_buf_initialize                        0.0406
    24 _xfs_buf_lookup_pages                      0.0179
    24 vunmap_page_range                          0.0250 <- vunmap
    23 find_lock_page                             0.0799
    22 vm_map_ram                                 0.0087 <- vmap
    20 kfree                                      0.0125
    19 put_page                                   0.0330
    18 __kmalloc                                  0.0176
    17 xfs_da_node_lookup_int                     0.0086
    17 _read_lock                                 0.0885
    17 page_waitqueue                             0.0664

vmap has gone from being the top 5 on the profiles and flushing the crap
out of all TLBs, to using less than 1% of kernel time.

[akpm@linux-foundation.org: cleanups, section fix]
[akpm@linux-foundation.org: fix build on alpha]
Signed-off-by: NNick Piggin <npiggin@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      db64fe02
  17. 09 10月, 2008 1 次提交
    • J
      xen: use spin_lock_nest_lock when pinning a pagetable · eefb47f6
      由 Jeremy Fitzhardinge 提交于 
      When pinning/unpinning a pagetable with split pte locks, we can end up
holding multiple pte locks at once (we need to hold the locks while
there's a pending batched hypercall affecting the pte page).  Because
all the pte locks are in the same lock class, lockdep thinks that
we're potentially taking a lock recursively.

This warning is spurious because we always take the pte locks while
holding mm->page_table_lock.  lockdep now has spin_lock_nest_lock to
express this kind of dominant lock use, so use it here so that lockdep
knows what's going on.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      eefb47f6
  19. 10 9月, 2008 1 次提交
  21. 21 8月, 2008 1 次提交
  23. 20 8月, 2008 2 次提交
  25. 22 7月, 2008 2 次提交
  27. 16 7月, 2008 9 次提交
    • J
      xen64: allocate and manage user pagetables · d6182fbf
      由 Jeremy Fitzhardinge 提交于 
      Because the x86_64 architecture does not enforce segment limits, Xen
cannot protect itself with them as it does in 32-bit mode.  Therefore,
to protect itself, it runs the guest kernel in ring 3.  Since it also
runs the guest userspace in ring3, the guest kernel must maintain a
second pagetable for its userspace, which does not map kernel space.
Naturally, the guest kernel pagetables map both kernel and userspace.

The userspace pagetable is attached to the corresponding kernel
pagetable via the pgd's page->private field.  It is allocated and
freed at the same time as the kernel pgd via the
paravirt_pgd_alloc/free hooks.

Fortunately, the user pagetable is almost entirely shared with the
kernel pagetable; the only difference is the pgd page itself.  set_pgd
will populate all entries in the kernel pagetable, and also set the
corresponding user pgd entry if the address is less than
STACK_TOP_MAX.

The user pagetable must be pinned and unpinned with the kernel one,
but because the pagetables are aliased, pgd_walk() only needs to be
called on the kernel pagetable.  The user pgd page is then
pinned/unpinned along with the kernel pgd page.

xen_write_cr3 must write both the kernel and user cr3s.

The init_mm.pgd pagetable never has a user pagetable allocated for it,
because it can never be used while running usermode.

One awkward area is that early in boot the page structures are not
available.  No user pagetable can exist at that point, but it
complicates the logic to avoid looking at the page structure.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d6182fbf
    • J
      xen: rework pgd_walk to deal with 32/64 bit · 5deb30d1
      由 Jeremy Fitzhardinge 提交于 
      Rewrite pgd_walk to deal with 64-bit address spaces.  There are two
notible features of 64-bit workspaces:

 1. The physical address is only 48 bits wide, with the upper 16 bits
    being sign extension; kernel addresses are negative, and userspace is
    positive.

 2. The Xen hypervisor mapping is at the negative-most address, just above
    the sign-extension hole.

1. means that we can't easily use addresses when traversing the space,
since we must deal with sign extension.  This rewrite expresses
everything in terms of pgd/pud/pmd indices, which means we don't need
to worry about the exact configuration of the virtual memory space.
This approach works equally well in 32-bit.

To deal with 2, assume the hole is between the uppermost userspace
address and PAGE_OFFSET.  For 64-bit this skips the Xen mapping hole.
For 32-bit, the hole is zero-sized.

In all cases, the uppermost kernel address is FIXADDR_TOP.

A side-effect of this patch is that the upper boundary is actually
handled properly, exposing a long-standing bug in 32-bit, which failed
to pin kernel pmd page.  The kernel pmd is not shared, and so must be
explicitly pinned, even though the kernel ptes are shared and don't
need pinning.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      5deb30d1
    • J
      xen: use set_pte_vaddr · 836fe2f2
      由 Jeremy Fitzhardinge 提交于 
      Make Xen's set_pte_mfn() use set_pte_vaddr rather than copying it.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NMark McLoughlin <markmc@redhat.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      836fe2f2
    • J
      xen64: use arbitrary_virt_to_machine for xen_set_pmd · ce803e70
      由 Jeremy Fitzhardinge 提交于 
      When building initial pagetables in 64-bit kernel the pud/pmd pointer may
be in ioremap/fixmap space, so we need to walk the pagetable to look up the
physical address.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      ce803e70
    • J
      xen: fix truncation of machine address · ebd879e3
      由 Jeremy Fitzhardinge 提交于 
      arbitrary_virt_to_machine can truncate a machine address if its above
4G.  Cast the problem away.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      ebd879e3
    • J
      xen64: get active_mm from the pda · ce87b3d3
      由 Jeremy Fitzhardinge 提交于 
      x86_64 stores the active_mm in the pda, so fetch it from there.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      ce87b3d3
    • J
      xen64: add extra pv_mmu_ops · f6e58732
      由 Jeremy Fitzhardinge 提交于 
      We need extra pv_mmu_ops for 64-bit, to deal with the extra level of
pagetable.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f6e58732
    • J
      x86: use __page_aligned_data/bss · cbcd79c2
      由 Jeremy Fitzhardinge 提交于 
      Update arch/x86's use of page-aligned variables.  The change to
arch/x86/xen/mmu.c fixes an actual bug, but the rest are cleanups
and to set a precedent.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      cbcd79c2
    • E
      pvops-64: call paravirt_post_allocator_init() on setup_arch() · c1f2f09e
      由 Eduardo Habkost 提交于 
      Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c1f2f09e
  29. 04 7月, 2008 1 次提交
  31. 26 6月, 2008 1 次提交
  33. 25 6月, 2008 2 次提交
    • J
      xen: add mechanism to extend existing multicalls · 400d3494
      由 Jeremy Fitzhardinge 提交于 
      Some Xen hypercalls accept an array of operations to work on.  In
general this is because its more efficient for the hypercall to the
work all at once rather than as separate hypercalls (even batched as a
multicall).

This patch adds a mechanism (xen_mc_extend_args()) to allocate more
argument space to the last-issued multicall, in order to extend its
argument list.

The user of this mechanism is xen/mmu.c, which uses it to extend the
args array of mmu_update.  This is particularly valuable when doing
the update for a large mprotect, which goes via
ptep_modify_prot_commit(), but it also manages to batch updates to
pgd/pmds as well.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      400d3494
    • J
      xen: implement ptep_modify_prot_start/commit · e57778a1
      由 Jeremy Fitzhardinge 提交于 
      Xen has a pte update function which will update a pte while preserving
its accessed and dirty bits.  This means that ptep_modify_prot_start() can be
implemented as a simple read of the pte value.  The hardware may
update the pte in the meantime, but ptep_modify_prot_commit() updates it while
preserving any changes that may have happened in the meantime.

The updates in ptep_modify_prot_commit() are batched if we're currently in lazy
mmu mode.

The mmu_update hypercall can take a batch of updates to perform, but
this code doesn't make particular use of that feature, in favour of
using generic multicall batching to get them all into the hypervisor.

The net effect of this is that each mprotect pte update turns from two
expensive trap-and-emulate faults into they hypervisor into a single
hypercall whose cost is amortized in a batched multicall.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e57778a1
  35. 24 6月, 2008 1 次提交
  37. 20 6月, 2008 4 次提交
  39. 02 6月, 2008 2 次提交
  41. 28 5月, 2008 1 次提交
    • I
      xen: fix early bootup crash on native hardware · b20aeccd
      由 Ingo Molnar 提交于 
      -tip tree auto-testing found the following early bootup hang:

-------------->
get_memcfg_from_srat: assigning address to rsdp
RSD PTR  v0 [Nvidia]
BUG: Int 14: CR2 ffd00040
     EDI 8092fbfe  ESI ffd00040  EBP 80b0aee8  ESP 80b0aed0
     EBX 000f76f0  EDX 0000000e  ECX 00000003  EAX ffd00040
     err 00000000  EIP 802c055a   CS 00000060  flg 00010006
Stack: ffd00040 80bc78d0 80b0af6c 80b1dbfe 8093d8ba 00000008 80b42810 80b4ddb4
       80b42842 00000000 80b0af1c 801079c8 808e724e 00000000 80b42871 802c0531
       00000100 00000000 0003fff0 80b0af40 80129999 00040100 00040100 00000000
Pid: 0, comm: swapper Not tainted 2.6.26-rc4-sched-devel.git #570
 [<802c055a>] ? strncmp+0x11/0x25
 [<80b1dbfe>] ? get_memcfg_from_srat+0xb4/0x568
 [<801079c8>] ? mcount_call+0x5/0x9
 [<802c0531>] ? strcmp+0xa/0x22
 [<80129999>] ? printk+0x38/0x3a
 [<80129999>] ? printk+0x38/0x3a
 [<8011b122>] ? memory_present+0x66/0x6f
 [<80b216b4>] ? setup_memory+0x13/0x40c
 [<80b16b47>] ? propagate_e820_map+0x80/0x97
 [<80b1622a>] ? setup_arch+0x248/0x477
 [<80129999>] ? printk+0x38/0x3a
 [<80b11759>] ? start_kernel+0x6e/0x2eb
 [<80b110fc>] ? i386_start_kernel+0xeb/0xf2
 =======================
<------

with this config:

   http://redhat.com/~mingo/misc/config-Wed_May_28_01_33_33_CEST_2008.bad

The thing is, the crash makes little sense at first sight. We crash on a
benign-looking printk. The code around it got changed in -tip but
checking those topic branches individually did not reproduce the bug.

Bisection led to this commit:

|   d5edbc1f is first bad commit
|   commit d5edbc1f
|   Author: Jeremy Fitzhardinge <jeremy@goop.org>
|   Date:   Mon May 26 23:31:22 2008 +0100
|
|   xen: add p2m mfn_list_list

Which is somewhat surprising, as on native hardware Xen client side
should have little to no side-effects.

After some head scratching, it turns out the following happened:
randconfig enabled the following Xen options:

  CONFIG_XEN=y
  CONFIG_XEN_MAX_DOMAIN_MEMORY=8
  # CONFIG_XEN_BLKDEV_FRONTEND is not set
  # CONFIG_XEN_NETDEV_FRONTEND is not set
  CONFIG_HVC_XEN=y
  # CONFIG_XEN_BALLOON is not set

which activated this piece of code in arch/x86/xen/mmu.c:

> @@ -69,6 +69,13 @@
>  	__attribute__((section(".data.page_aligned"))) =
>  		{ [ 0 ... TOP_ENTRIES - 1] = &p2m_missing[0] };
>
> +/* Arrays of p2m arrays expressed in mfns used for save/restore */
> +static unsigned long p2m_top_mfn[TOP_ENTRIES]
> +	__attribute__((section(".bss.page_aligned")));
> +
> +static unsigned long p2m_top_mfn_list[TOP_ENTRIES / P2M_ENTRIES_PER_PAGE]
> +	__attribute__((section(".bss.page_aligned")));

The problem is, you must only put variables into .bss.page_aligned that
have a _size_ that is _exactly_ page aligned. In this case the size of
p2m_top_mfn_list is not page aligned:

 80b8d000 b p2m_top_mfn
 80b8f000 b p2m_top_mfn_list
 80b8f008 b softirq_stack
 80b97008 b hardirq_stack
 80b9f008 b bm_pte

So all subsequent variables get unaligned which, depending on luck,
breaks the kernel in various funny ways. In this case what killed the
kernel first was the misaligned bootmap pte page, resulting in that
creative crash above.

Anyway, this was a fun bug to track down :-)

I think the moral is that .bss.page_aligned is a dangerous construct in
its current form, and the symptoms of breakage are very non-trivial, so
i think we need build-time checks to make sure all symbols in
.bss.page_aligned are truly page aligned.

The Xen fix below gets the kernel booting again.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      b20aeccd
  43. 27 5月, 2008 2 次提交
    • J
      xen: implement save/restore · 0e91398f
      由 Jeremy Fitzhardinge 提交于 
      This patch implements Xen save/restore and migration.

Saving is triggered via xenbus, which is polled in
drivers/xen/manage.c.  When a suspend request comes in, the kernel
prepares itself for saving by:

1 - Freeze all processes.  This is primarily to prevent any
    partially-completed pagetable updates from confusing the suspend
    process.  If CONFIG_PREEMPT isn't defined, then this isn't necessary.

2 - Suspend xenbus and other devices

3 - Stop_machine, to make sure all the other vcpus are quiescent.  The
    Xen tools require the domain to run its save off vcpu0.

4 - Within the stop_machine state, it pins any unpinned pgds (under
    construction or destruction), performs canonicalizes various other
    pieces of state (mostly converting mfns to pfns), and finally

5 - Suspend the domain

Restore reverses the steps used to save the domain, ending when all
the frozen processes are thawed.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      0e91398f
    • J
      xen: add p2m mfn_list_list · d5edbc1f
      由 Jeremy Fitzhardinge 提交于 
      When saving a domain, the Xen tools need to remap all our mfns to
portable pfns.  In order to remap our p2m table, it needs to know
where all its pages are, so maintain the references to the p2m table
for it to use.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      d5edbc1f