[PATCH] arm64/kvm: Fix zapping stage2 page table wrongly

[Gavin Shan <gshan@redhat.com>]

Depending on the kernel configuration, PUD_SIZE could be equal to
PMD_SIZE. For example, both of them are 512MB with the following
kernel configuration. In this case, both PUD and PMD are folded
to PGD.

   CONFIG_ARM64_64K_PAGES   y
   CONFIG_ARM64_VA_BITS     42
   CONFIG_PGTABLE_LEVELS    2

With the above configuration, the stage2 PUD is used to backup the
512MB huge page when the stage2 mapping is built. During the mapping,
the PUD and its subordinate levels of page table entries are unmapped
if the PUD is present and not huge page sensitive in stage2_set_pud_huge().
Unfornately, the @addr isn't aligned to S2_PUD_SIZE and wrong page table
entries are zapped. It eventually leads to PUD's present bit can't be
cleared successfully and infinite loop in stage2_set_pud_huge().

This fixes the issue by checking with S2_{PUD, PMD}_SIZE instead of
{PUD, PMD}_SIZE to determine if stage2 PUD or PMD is used to back the
huge page. For this particular case, the stage2 PMD entry should be
used to backup the 512MB huge page with stage2_set_pmd_huge().

Fixes: 3c3736cd32bf ("KVM: arm/arm64: Fix handling of stage2 huge mappings")
Cc: stable@vger.kernel.org # v5.1+
Reported-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
 arch/arm64/kvm/mmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 0121ef2c7c8d..deb1819ba9e2 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1964,7 +1964,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		(fault_status == FSC_PERM &&
 		 stage2_is_exec(mmu, fault_ipa, vma_pagesize));
 
-	if (vma_pagesize == PUD_SIZE) {
+	if (vma_pagesize == S2_PUD_SIZE) {
 		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
 
 		new_pud = kvm_pud_mkhuge(new_pud);
@@ -1975,7 +1975,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			new_pud = kvm_s2pud_mkexec(new_pud);
 
 		ret = stage2_set_pud_huge(mmu, memcache, fault_ipa, &new_pud);
-	} else if (vma_pagesize == PMD_SIZE) {
+	} else if (vma_pagesize == S2_PMD_SIZE) {
 		pmd_t new_pmd = kvm_pfn_pmd(pfn, mem_type);
 
 		new_pmd = kvm_pmd_mkhuge(new_pmd);
-- 
2.23.0

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