From 9753f529156d03112d1ff6f3758ccd6fa6faf189 Mon Sep 17 00:00:00 2001 From: Lan Tianyu Date: Sun, 13 Mar 2016 11:10:24 +0800 Subject: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() There is already a barrier inside of kvm_flush_remote_tlbs() which can help to make sure everyone sees our modifications to the page tables and see changes to vcpu->mode here. So remove the smp_mb in the kvm_mmu_commit_zap_page() and update the comment. Signed-off-by: Lan Tianyu Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index e46a81f4856e..fc8ab1f67d00 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2390,14 +2390,13 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, return; /* - * wmb: make sure everyone sees our modifications to the page tables - * rmb: make sure we see changes to vcpu->mode - */ - smp_mb(); - - /* - * Wait for all vcpus to exit guest mode and/or lockless shadow - * page table walks. + * We need to make sure everyone sees our modifications to + * the page tables and see changes to vcpu->mode here. The barrier + * in the kvm_flush_remote_tlbs() achieves this. This pairs + * with vcpu_enter_guest and walk_shadow_page_lockless_begin/end. + * + * In addition, kvm_flush_remote_tlbs waits for all vcpus to exit + * guest mode and/or lockless shadow page table walks. */ kvm_flush_remote_tlbs(kvm); -- 2.34.1