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Two fixes to fix a memory corruption bug when WC pages never get

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converted back to WB but end up being recycled in the general memory
 pool as WC.
 
 Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Merge tag 'stable/for-linus-fixes-3.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Two fixes to fix a memory corruption bug when WC pages never get
converted back to WB but end up being recycled in the general memory
pool as WC.

There is a better way of fixing this, but there is not enough time to do
the full benchmarking to pick one of the right options - so picking the
one that favors stability for right now.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

* tag 'stable/for-linus-fixes-3.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/pat: Disable PAT support for now.
  xen/setup: Remove redundant filtering of PTE masks.
This commit is contained in:
Linus Torvalds 2012-02-26 21:03:16 -08:00
commit 500dd2370e
2 changed files with 6 additions and 8 deletions
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6
arch/x86/xen/enlighten.c
View File

@ -1141,7 +1141,9 @@ asmlinkage void __init xen_start_kernel(void)
/* Prevent unwanted bits from being set in PTEs. */
__supported_pte_mask &= ~_PAGE_GLOBAL;
#if 0
if (!xen_initial_domain())
#endif
__supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
__supported_pte_mask |= _PAGE_IOMAP;
@ -1204,10 +1206,6 @@ asmlinkage void __init xen_start_kernel(void)
pgd = (pgd_t *)xen_start_info->pt_base;
if (!xen_initial_domain())
__supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
__supported_pte_mask |= _PAGE_IOMAP;
/* Don't do the full vcpu_info placement stuff until we have a
possible map and a non-dummy shared_info. */
per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];

8
arch/x86/xen/mmu.c
View File

@ -415,13 +415,13 @@ static pteval_t iomap_pte(pteval_t val)
static pteval_t xen_pte_val(pte_t pte)
{
pteval_t pteval = pte.pte;
#if 0
/* If this is a WC pte, convert back from Xen WC to Linux WC */
if ((pteval & (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)) == _PAGE_PAT) {
WARN_ON(!pat_enabled);
pteval = (pteval & ~_PAGE_PAT) | _PAGE_PWT;
}
#endif
if (xen_initial_domain() && (pteval & _PAGE_IOMAP))
return pteval;
@ -463,7 +463,7 @@ void xen_set_pat(u64 pat)
static pte_t xen_make_pte(pteval_t pte)
{
phys_addr_t addr = (pte & PTE_PFN_MASK);
#if 0
/* If Linux is trying to set a WC pte, then map to the Xen WC.
* If _PAGE_PAT is set, then it probably means it is really
* _PAGE_PSE, so avoid fiddling with the PAT mapping and hope
@ -476,7 +476,7 @@ static pte_t xen_make_pte(pteval_t pte)
if ((pte & (_PAGE_PCD | _PAGE_PWT)) == _PAGE_PWT)
pte = (pte & ~(_PAGE_PCD | _PAGE_PWT)) | _PAGE_PAT;
}
#endif
/*
* Unprivileged domains are allowed to do IOMAPpings for
* PCI passthrough, but not map ISA space. The ISA