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KVM: arm/arm64: Skip updating PTE entry if no change 

When there is contention on faulting in a particular page table entry
at stage 2, the break-before-make requirement of the architecture can
lead to additional refaulting due to TLB invalidation.

Avoid this by skipping a page table update if the new value of the PTE
matches the previous value.

Cc: stable@vger.kernel.org
Fixes: d5d8184d35 ("KVM: ARM: Memory virtualization setup")
Reviewed-by: Suzuki Poulose <suzuki.poulose@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Punit Agrawal 2018-08-13 11:43:51 +01:00 committed by Marc Zyngier
parent 86658b819c
commit 976d34e2da
1 changed files with 4 additions and 0 deletions
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4
virt/kvm/arm/mmu.c
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@ -1147,6 +1147,10 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
/* Create 2nd stage page table mapping - Level 3 */ /* Create 2nd stage page table mapping - Level 3 */
old_pte = *pte; old_pte = *pte;
if (pte_present(old_pte)) { if (pte_present(old_pte)) {
/* Skip page table update if there is no change */
if (pte_val(old_pte) == pte_val(*new_pte))
return 0;
kvm_set_pte(pte, __pte(0)); kvm_set_pte(pte, __pte(0));
kvm_tlb_flush_vmid_ipa(kvm, addr); kvm_tlb_flush_vmid_ipa(kvm, addr);
} else { } else {