From: "Longpeng(Mike)" <longpeng2@huawei.com>
Date: Tue, 8 Aug 2017 12:05:33 +0800
Subject: KVM: X86: implement the logic for spinlock optimization
Patch-mainline: v4.14-rc1
Git-commit: de63ad4cf4973462953c29c363f3cfa7117c2b2d
References: bsc#1077761

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@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
---
 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(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -689,6 +689,9 @@
 
 	/* 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 {
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1274,7 +1274,7 @@
 
 	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:
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3667,7 +3667,10 @@
 
 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;
 }
 
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6764,7 +6764,13 @@
 	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 set PLE if supported,
+	 * 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);
 }
 
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2874,6 +2874,10 @@
 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()
@@ -7986,6 +7990,7 @@
 	kvm_pmu_init(vcpu);
 
 	vcpu->arch.pending_external_vector = -1;
+	vcpu->arch.preempted_in_kernel = false;
 
 	kvm_hv_vcpu_init(vcpu);
 
@@ -8435,7 +8440,7 @@
 
 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)