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KVM: arm/arm64: Fix handling of stage2 huge mappings

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We rely on the mmu_notifier call backs to handle the split/merge
of huge pages and thus we are guaranteed that, while creating a
block mapping, either the entire block is unmapped at stage2 or it
is missing permission.

However, we miss a case where the block mapping is split for dirty
logging case and then could later be made block mapping, if we cancel the
dirty logging. This not only creates inconsistent TLB entries for
the pages in the the block, but also leakes the table pages for
PMD level.

Handle this corner case for the huge mappings at stage2 by
unmapping the non-huge mapping for the block. This could potentially
release the upper level table. So we need to restart the table walk
once we unmap the range.

Fixes : ad361f093c ("KVM: ARM: Support hugetlbfs backed huge pages")
Reported-by: Zheng Xiang <zhengxiang9@huawei.com>
Cc: Zheng Xiang <zhengxiang9@huawei.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Suzuki K Poulose
2019-03-20 14:57:19 +00:00
committed by Marc Zyngier
parent a80868f398
commit 3c3736cd32
2 changed files with 45 additions and 16 deletions
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2
arch/arm/include/asm/stage2_pgtable.h
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@@ -75,6 +75,8 @@ static inline bool kvm_stage2_has_pud(struct kvm *kvm)
#define S2_PMD_MASK PMD_MASK
#define S2_PMD_SIZE PMD_SIZE
#define S2_PUD_MASK PUD_MASK
#define S2_PUD_SIZE PUD_SIZE
static inline bool kvm_stage2_has_pmd(struct kvm *kvm)
{