From 24fa4a211e2655ba71f0da7e351475bb8f752e93 Mon Sep 17 00:00:00 2001 From: Punit Agrawal Date: Mon, 13 Aug 2018 11:43:51 +0100 Subject: [PATCH] KVM: arm/arm64: Skip updating PTE entry if no change commit 976d34e2dab10ece5ea8fe7090b7692913f89084 upstream. 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: d5d8184d35c9 ("KVM: ARM: Memory virtualization setup") Reviewed-by: Suzuki Poulose Acked-by: Christoffer Dall Signed-off-by: Punit Agrawal Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman --- arch/arm/kvm/mmu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index e8835d4e173c..cd1779bf6ef7 100644 --- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -961,6 +961,10 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache, /* Create 2nd stage page table mapping - Level 3 */ old_pte = *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_tlb_flush_vmid_ipa(kvm, addr); } else {