4.4-stable 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.
Cc: stable@vger.kernel.org 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm/kvm/mmu.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -961,6 +961,10 @@ 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 {