<gregkh@xxxxxxxxxxxxxxxxxxx> writes:
> 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>.
This patch fails to apply for similar reason as to the PMD one I just
sent out. Please find the backport patch below.
Thanks,
Punit
-- >8 --
From: Punit Agrawal <punit.agrawal@xxxxxxx>
Date: Fri, 10 Aug 2018 20:05:07 +0100
Subject: [PATCH 2/2] 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.
Fixes: d5d8184d35c9 ("KVM: ARM: Memory virtualization setup")
Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx>
Reviewed-by: Suzuki Poulose <suzuki.poulose@xxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
---
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 e3acb3a6ca37..b3d268a79f05 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -978,6 +978,10 @@ 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 {
--
2.18.0
