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xen: don't map missing memory

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When setting up a pte for a missing pfn (no matching mfn), just create
an empty pte rather than a junk mapping.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
This commit is contained in:
Jeremy Fitzhardinge
2010-08-31 14:06:22 -07:00
parent 33a847502b
commit cfd8951e08
2 changed files with 22 additions and 2 deletions
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15
arch/x86/xen/mmu.c
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@@ -745,7 +745,20 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
if (val & _PAGE_PRESENT) {
unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
pteval_t flags = val & PTE_FLAGS_MASK;
val = ((pteval_t)pfn_to_mfn(pfn) << PAGE_SHIFT) | flags;
unsigned long mfn = pfn_to_mfn(pfn);
/*
* If there's no mfn for the pfn, then just create an
* empty non-present pte. Unfortunately this loses
* information about the original pfn, so
* pte_mfn_to_pfn is asymmetric.
*/
if (unlikely(mfn == INVALID_P2M_ENTRY)) {
mfn = 0;
flags = 0;
}
val = ((pteval_t)mfn << PAGE_SHIFT) | flags;
}
return val;