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iommu/amd: Fix downgrading default page-sizes in alloc_pte() 

Downgrading an existing large mapping to a mapping using smaller
page-sizes works only for the mappings created with page-mode 7 (i.e.
non-default page size).

Treat large mappings created with page-mode 0 (i.e. default page size)
like a non-present mapping and allow to overwrite it in alloc_pte().

While around, make sure that we flush the TLB only if we change an
existing mapping, otherwise we might end up acting on garbage PTEs.

Fixes: 6d568ef9a6 ("iommu/amd: Allow downgrading page-sizes in alloc_pte()")
Signed-off-by: Andrei Dulea <adulea@amazon.de>
This commit is contained in:
Andrei Dulea 2019-09-13 16:42:29 +02:00 committed by Joerg Roedel
parent 34c0989c05
commit 6ccb72f837
1 changed files with 2 additions and 1 deletions
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3
drivers/iommu/amd_iommu.c
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@ -1490,6 +1490,7 @@ static u64 *alloc_pte(struct protection_domain *domain,
pte_level = PM_PTE_LEVEL(__pte);
if (!IOMMU_PTE_PRESENT(__pte) ||
pte_level == PAGE_MODE_NONE ||
pte_level == PAGE_MODE_7_LEVEL) {
page = (u64 *)get_zeroed_page(gfp);
if (!page)
@ -1500,7 +1501,7 @@ static u64 *alloc_pte(struct protection_domain *domain,
/* pte could have been changed somewhere. */
if (cmpxchg64(pte, __pte, __npte) != __pte)
free_page((unsigned long)page);
else if (pte_level == PAGE_MODE_7_LEVEL)
else if (IOMMU_PTE_PRESENT(__pte))
domain->updated = true;
continue;