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| author | David Vrabel <david.vrabel@citrix.com> | 2012-07-09 12:39:06 +0200 |
|---|---|---|
| committer | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2012-07-19 21:51:44 +0200 |
| commit | 66a27dde9ae96e35278983f2e59bea04eb714cd0 (patch) | |
| tree | 17e7b1054153131a11ef9f437787424be5b901f1 /arch/x86 | |
| parent | xen/mm: do direct hypercall in xen_set_pte() if batching is unavailable (diff) | |
| download | linux-66a27dde9ae96e35278983f2e59bea04eb714cd0.tar.xz linux-66a27dde9ae96e35278983f2e59bea04eb714cd0.zip | |
xen/mm: zero PTEs for non-present MFNs in the initial page table
When constructing the initial page tables, if the MFN for a usable PFN
is missing in the p2m then that frame is initially ballooned out. In
this case, zero the PTE (as in decrease_reservation() in
drivers/xen/balloon.c).
This is obviously safe instead of having an valid PTE with an MFN of
INVALID_P2M_ENTRY (~0).
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/xen/mmu.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 3f1783a79a3c..27336dfcda8e 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1432,6 +1432,10 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) * Init-time set_pte while constructing initial pagetables, which * doesn't allow RO page table pages to be remapped RW. * + * If there is no MFN for this PFN then this page is initially + * ballooned out so clear the PTE (as in decrease_reservation() in + * drivers/xen/balloon.c). + * * Many of these PTE updates are done on unpinned and writable pages * and doing a hypercall for these is unnecessary and expensive. At * this point it is not possible to tell if a page is pinned or not, @@ -1440,7 +1444,10 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) */ static void __init xen_set_pte_init(pte_t *ptep, pte_t pte) { - pte = mask_rw_pte(ptep, pte); + if (pte_mfn(pte) != INVALID_P2M_ENTRY) + pte = mask_rw_pte(ptep, pte); + else + pte = __pte_ma(0); native_set_pte(ptep, pte); } |