| From | Ben Hutchings <> | Date | Sun, 09 Dec 2018 21:50:33 +0000 | Subject | [PATCH 3.16 134/328] KVM: arm/arm64: Skip updating PTE entry if no change |
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3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: Punit Agrawal <punit.agrawal@arm.com>
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") 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> [bwh: Backported to 3.16: adjust filename] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- arch/arm/kvm/mmu.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -758,6 +758,10 @@ static int stage2_set_pte(struct kvm *kv /* 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 {
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