linux-kernel - [PATCH v2 3/3] KVM: SVM: Fix disable pause loop exit/pause filtering capability on SVM

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Date:   Tue, 28 Jul 2020 17:45:06 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: [PATCH v2 3/3] KVM: SVM: Fix disable pause loop exit/pause filtering capability on SVM

From: Wanpeng Li <wanpengli@...cent.com>

Commit 8566ac8b (KVM: SVM: Implement pause loop exit logic in SVM) drops
disable pause loop exit/pause filtering capability completely, I guess it
is a merge fault by Radim since disable vmexits capabilities and pause
loop exit for SVM patchsets are merged at the same time. This patch
reintroduces the disable pause loop exit/pause filtering capability
support.

We can observe 2.9% hackbench improvement for a 92 vCPUs guest on AMD 
Rome Server.

Reported-by: Haiwei Li <lihaiwei@...cent.com>
Tested-by: Haiwei Li <lihaiwei@...cent.com>
Fixes: 8566ac8b (KVM: SVM: Implement pause loop exit logic in SVM)
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kvm/svm/svm.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c0da4dd..c20f127 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1090,7 +1090,7 @@ static void init_vmcb(struct vcpu_svm *svm)
 	svm->nested.vmcb = 0;
 	svm->vcpu.arch.hflags = 0;
 
-	if (pause_filter_count) {
+	if (pause_filter_count && !kvm_pause_in_guest(svm->vcpu.kvm)) {
 		control->pause_filter_count = pause_filter_count;
 		if (pause_filter_thresh)
 			control->pause_filter_thresh = pause_filter_thresh;
@@ -2693,7 +2693,7 @@ static int pause_interception(struct vcpu_svm *svm)
 	struct kvm_vcpu *vcpu = &svm->vcpu;
 	bool in_kernel = (svm_get_cpl(vcpu) == 0);
 
-	if (pause_filter_thresh)
+	if (!kvm_pause_in_guest(vcpu->kvm))
 		grow_ple_window(vcpu);
 
 	kvm_vcpu_on_spin(vcpu, in_kernel);
@@ -3780,7 +3780,7 @@ static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu)
 
 static void svm_sched_in(struct kvm_vcpu *vcpu, int cpu)
 {
-	if (pause_filter_thresh)
+	if (!kvm_pause_in_guest(vcpu->kvm))
 		shrink_ple_window(vcpu);
 }
 
@@ -3958,6 +3958,9 @@ static void svm_vm_destroy(struct kvm *kvm)
 
 static int svm_vm_init(struct kvm *kvm)
 {
+	if (!pause_filter_thresh)
+		kvm->arch.pause_in_guest = true;
+
 	if (avic) {
 		int ret = avic_vm_init(kvm);
 		if (ret)
-- 
2.7.4