The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 976d34e2dab10ece5ea8fe7090b7692913f89084 Mon Sep 17 00:00:00 2001
From: Punit Agrawal <punit.agrawal@xxxxxxx>
Date: Mon, 13 Aug 2018 11:43:51 +0100
Subject: [PATCH] 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@xxxxxxxxxxxxxxx
Fixes: d5d8184d35c9 ("KVM: ARM: Memory virtualization setup")
Reviewed-by: Suzuki Poulose <suzuki.poulose@xxxxxxx>
Acked-by: Christoffer Dall <christoffer.dall@xxxxxxx>
Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 13dfe36501aa..91aaf73b00df 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -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 */
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 {
