From: Lan Tianyu <tianyu.lan@intel.com>
To: gleb@kernel.org, pbonzini@redhat.com, tglx@linutronix.de,
mingo@redhat.com, hpa@zytor.com, x86@kernel.org,
guangrong.xiao@linux.intel.com
Cc: Lan Tianyu <tianyu.lan@intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/7] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page()
Date: Sun, 13 Mar 2016 11:10:24 +0800 [thread overview]
Message-ID: <1457838631-26775-2-git-send-email-tianyu.lan@intel.com> (raw)
In-Reply-To: <1457838631-26775-1-git-send-email-tianyu.lan@intel.com>
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 <tianyu.lan@intel.com>
---
arch/x86/kvm/mmu.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 2463de0..5e795af 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2390,14 +2390,12 @@ 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() helps us to achieve these. This pairs
+ * with vcpu_enter_guest and walk_shadow_page_lockless_begin/end.
+ * In addition, wait for all vcpus to exit guest mode and/or lockless
+ * shadow page table walks.
*/
kvm_flush_remote_tlbs(kvm);
--
1.8.4.rc0.1.g8f6a3e5.dirty
next prev parent reply other threads:[~2016-03-13 3:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-13 3:10 [PATCH 0/7] KVM/X86/PPC: Clear up kvm mmu memory barriers and update related comments Lan Tianyu
2016-03-13 3:10 ` Lan Tianyu [this message]
2016-03-13 3:10 ` [PATCH 2/7] KVM/x86: Replace smp_mb() with smp_store_mb/release() in the walk_shadow_page_lockless_begin/end() Lan Tianyu
2016-03-13 3:10 ` [PATCH 3/7] KVM: Replace smp_mb() with smp_mb_after_atomic() in the kvm_make_all_cpus_request() Lan Tianyu
2016-03-13 3:10 ` [PATCH 4/7] KVM/x86: Call smp_wmb() before increasing tlbs_dirty Lan Tianyu
2016-03-13 3:10 ` [PATCH 5/7] KVM: Replace smp_mb() with smp_load_acquire() in the kvm_flush_remote_tlbs() Lan Tianyu
2016-03-13 3:10 ` [PATCH 6/7] KVM/x86: update the comment of memory barrier in the vcpu_enter_guest() Lan Tianyu
2016-03-13 3:10 ` [PATCH 7/7] KVM/PPC: update the comment of memory barrier in the kvmppc_prepare_to_enter() Lan Tianyu
2016-03-14 13:03 ` [PATCH 0/7] KVM/X86/PPC: Clear up kvm mmu memory barriers and update related comments Paolo Bonzini
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