[PATCH AUTOSEL 5.2 32/63] iommu/amd: Fix downgrading default page-sizes in alloc_pte()

Sasha Levin
2019-10-01T16:42:17Z

From: Andrei Dulea <adulea@amazon.de>

[ Upstream commit 6ccb72f8374e17d60b58a7bfd5570496332c54e2 ]

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: 6d568ef9a622 ("iommu/amd: Allow downgrading page-sizes in alloc_pte()")
Signed-off-by: Andrei Dulea <adulea@amazon.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/amd_iommu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 3e687f18b203a..f0fdc598f64dc 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1480,6 +1480,7 @@ 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)
@@ -1490,7 +1491,7 @@ 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;
--
2.20.1