[PATCH 2/4] KVM: X86: implement the logic for spinlock optimization

[Longpeng(Mike)]

get_cpl requires vcpu_load, so we must cache the result (whether the
vcpu was preempted when its cpl=0) in kvm_vcpu_arch.

Signed-off-by: Longpeng(Mike) <longpeng2@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h | 3 +++
 arch/x86/kvm/hyperv.c           | 2 +-
 arch/x86/kvm/svm.c              | 5 ++++-
 arch/x86/kvm/vmx.c              | 8 +++++++-
 arch/x86/kvm/x86.c              | 7 ++++++-
 5 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 87ac4fba6d8e..1679aabcabe5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -688,6 +688,9 @@ struct kvm_vcpu_arch {
 
 	/* GPA available (AMD only) */
 	bool gpa_available;
+
+	/* be preempted when it's in kernel-mode(cpl=0) */
+	bool preempted_in_kernel;
 };
 
 struct kvm_lpage_info {
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 5243d54f73ab..dc97f2544b6f 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1274,7 +1274,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	switch (code) {
 	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
-		kvm_vcpu_on_spin(vcpu, false);
+		kvm_vcpu_on_spin(vcpu, true);
 		break;
 	case HVCALL_POST_MESSAGE:
 	case HVCALL_SIGNAL_EVENT:
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0cc486fd9871..fc027f2e87d1 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3749,7 +3749,10 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
 
 static int pause_interception(struct vcpu_svm *svm)
 {
-	kvm_vcpu_on_spin(&svm->vcpu, false);
+	struct kvm_vcpu *vcpu = &svm->vcpu;
+	bool in_kernel = (svm_get_cpl(vcpu) == 0);
+
+	kvm_vcpu_on_spin(vcpu, in_kernel);
 	return 1;
 }
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fef784c22190..46d08b389e36 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6781,7 +6781,13 @@ static int handle_pause(struct kvm_vcpu *vcpu)
 	if (ple_gap)
 		grow_ple_window(vcpu);
 
-	kvm_vcpu_on_spin(vcpu, false);
+	/*
+	 * Intel sdm vol3 ch-25.1.3 says: The "PAUSE-loop exiting"
+	 * VM-execution control is ignored if CPL > 0. OTOH, KVM
+	 * never set PAUSE_EXITING and just only uses PLE,
+	 * so the vcpu must be CPL=0 if it gets a PAUSE exit.
+	 */
+	kvm_vcpu_on_spin(vcpu, true);
 	return kvm_skip_emulated_instruction(vcpu);
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aba9d038d09e..bee9ad0ed4cd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2873,6 +2873,10 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	int idx;
+
+	if (vcpu->preempted)
+		vcpu->arch.preempted_in_kernel = !kvm_x86_ops->get_cpl(vcpu);
+
 	/*
 	 * Disable page faults because we're in atomic context here.
 	 * kvm_write_guest_offset_cached() would call might_fault()
@@ -7985,6 +7989,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 	kvm_pmu_init(vcpu);
 
 	vcpu->arch.pending_external_vector = -1;
+	vcpu->arch.preempted_in_kernel = false;
 
 	kvm_hv_vcpu_init(vcpu);
 
@@ -8434,7 +8439,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 {
-	return false;
+	return vcpu->arch.preempted_in_kernel;
 }
 
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
-- 
1.8.3.1