linux/arch/x86/xen
Konrad Rzeszutek Wilk 8eaffa67b4 xen/pat: Disable PAT support for now.
[Pls also look at https://lkml.org/lkml/2012/2/10/228]

Using of PAT to change pages from WB to WC works quite nicely.
Changing it back to WB - not so much. The crux of the matter is
that the code that does this (__page_change_att_set_clr) has only
limited information so when it tries to the change it gets
the "raw" unfiltered information instead of the properly filtered one -
and the "raw" one tell it that PSE bit is on (while infact it
is not).  As a result when the PTE is set to be WB from WC, we get
tons of:

:WARNING: at arch/x86/xen/mmu.c:475 xen_make_pte+0x67/0xa0()
:Hardware name: HP xw4400 Workstation
.. snip..
:Pid: 27, comm: kswapd0 Tainted: G        W    3.2.2-1.fc16.x86_64 #1
:Call Trace:
: [<ffffffff8106dd1f>] warn_slowpath_common+0x7f/0xc0
: [<ffffffff8106dd7a>] warn_slowpath_null+0x1a/0x20
: [<ffffffff81005a17>] xen_make_pte+0x67/0xa0
: [<ffffffff810051bd>] __raw_callee_save_xen_make_pte+0x11/0x1e
: [<ffffffff81040e15>] ? __change_page_attr_set_clr+0x9d5/0xc00
: [<ffffffff8114c2e8>] ? __purge_vmap_area_lazy+0x158/0x1d0
: [<ffffffff8114cca5>] ? vm_unmap_aliases+0x175/0x190
: [<ffffffff81041168>] change_page_attr_set_clr+0x128/0x4c0
: [<ffffffff81041542>] set_pages_array_wb+0x42/0xa0
: [<ffffffff8100a9b2>] ? check_events+0x12/0x20
: [<ffffffffa0074d4c>] ttm_pages_put+0x1c/0x70 [ttm]
: [<ffffffffa0074e98>] ttm_page_pool_free+0xf8/0x180 [ttm]
: [<ffffffffa0074f78>] ttm_pool_mm_shrink+0x58/0x90 [ttm]
: [<ffffffff8112ba04>] shrink_slab+0x154/0x310
: [<ffffffff8112f17a>] balance_pgdat+0x4fa/0x6c0
: [<ffffffff8112f4b8>] kswapd+0x178/0x3d0
: [<ffffffff815df134>] ? __schedule+0x3d4/0x8c0
: [<ffffffff81090410>] ? remove_wait_queue+0x50/0x50
: [<ffffffff8112f340>] ? balance_pgdat+0x6c0/0x6c0
: [<ffffffff8108fb6c>] kthread+0x8c/0xa0

for every page. The proper fix for this is has been posted
and is https://lkml.org/lkml/2012/2/10/228
"x86/cpa: Use pte_attrs instead of pte_flags on CPA/set_p.._wb/wc operations."
along with a detailed description of the problem and solution.

But since that posting has gone nowhere I am proposing
this band-aid solution so that at least users don't get
the page corruption (the pages that are WC don't get changed to WB
and end up being recycled for filesystem or other things causing
mysterious crashes).

The negative impact of this patch is that users of WC flag
(which are InfiniBand, radeon, nouveau drivers) won't be able
to set that flag - so they are going to see performance degradation.
But stability is more important here.

Fixes RH BZ# 742032, 787403, and 745574
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-02-20 10:41:35 -05:00
..
debugfs.c switch debugfs to umode_t 2012-01-03 22:54:56 -05:00
debugfs.h switch debugfs to umode_t 2012-01-03 22:54:56 -05:00
enlighten.c xen/pat: Disable PAT support for now. 2012-02-20 10:41:35 -05:00
grant-table.c Merge commit 'v3.2-rc3' into stable/for-linus-3.3 2011-12-20 17:01:18 -05:00
irq.c arch/x86/xen/irq: Cleanup code/data sections definitions 2011-05-12 17:19:33 -04:00
Kconfig xen: Make XEN_MAX_DOMAIN_MEMORY have more sensible defaults 2011-11-21 17:14:46 -05:00
Makefile xen/tracing: Fix tracing config option properly 2011-08-22 11:28:33 -04:00
mmu.c xen/pat: Disable PAT support for now. 2012-02-20 10:41:35 -05:00
mmu.h xen: make a pile of mmu pvop functions static 2011-05-20 14:25:24 -07:00
multicalls.c xen/multicall: move *idx fields to start of mc_buffer 2011-07-18 15:43:46 -07:00
multicalls.h xen/trace: add multicall tracing 2011-07-18 15:43:26 -07:00
p2m.c Merge branches 'stable/bug.fixes-3.2' and 'stable/mmu.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2011-10-25 09:17:47 +02:00
pci-swiotlb-xen.c treewide: fix a few typos in comments 2011-05-10 10:16:21 +02:00
platform-pci-unplug.c xen:pvhvm: Modpost section mismatch fix 2011-07-11 13:37:04 -04:00
setup.c Merge branch 'memblock-kill-early_node_map' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc into core/memblock 2011-12-20 12:14:26 +01:00
smp.c xen/smp: Fix CPU online/offline bug triggering a BUG: scheduling while atomic. 2012-02-03 16:05:42 -05:00
spinlock.c x86: xen: size struct xen_spinlock to always fit in arch_spinlock_t 2012-01-24 12:10:19 -05:00
suspend.c xen: suspend: add "arch" to pre/post suspend hooks 2011-02-25 16:43:12 +00:00
time.c Merge branch 'upstream/xen-settime' of git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen 2011-11-06 20:15:05 -08:00
trace.c xen/trace: Fix compile error when CONFIG_XEN_PRIVILEGED_GUEST is not set 2011-08-05 09:43:02 -04:00
vdso.h
vga.c xen: allow enable use of VGA console on dom0 2011-06-06 11:46:00 -04:00
xen-asm.h xen: make direct versions of irq_enable/disable/save/restore to common code 2009-02-04 16:59:04 -08:00
xen-asm.S x86: style cleanups for xen assemblies 2009-02-05 20:25:41 +01:00
xen-asm_32.S xen: x86_32: do not enable iterrupts when returning from exception in interrupt context 2011-09-01 12:54:42 -04:00
xen-asm_64.S xen: use iret for return from 64b kernel to 32b usermode 2009-12-03 11:14:54 -08:00
xen-head.S x86, asm: Cleanup unnecssary macros in asm-offsets.c 2011-02-25 16:37:32 -08:00
xen-ops.h Merge branch 'stable/vga.support' into stable/drivers 2011-06-21 09:25:41 -04:00