[PATCH v3 11/12] KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC

[Maxim Levitsky]

Currently it is possible to have the following scenario:

1. AVIC is disabled by svm_refresh_apicv_exec_ctrl
2. svm_vcpu_blocking calls avic_vcpu_put which does nothing
3. svm_vcpu_unblocking enables the AVIC (due to KVM_REQ_APICV_UPDATE)
   and then calls avic_vcpu_load
4. warning is triggered in avic_vcpu_load since
   AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK was never cleared

While it is possible to just remove the warning, it seems to be more robust
to fully disable/enable AVIC in svm_refresh_apicv_exec_ctrl by calling the
avic_vcpu_load/avic_vcpu_put

Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
 arch/x86/kvm/svm/avic.c | 43 ++++++++++++++++++++++-------------------
 arch/x86/kvm/svm/svm.c  |  8 ++++++--
 arch/x86/kvm/x86.c      |  9 ++++++++-
 3 files changed, 37 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 1def54c26259..a39f7888b587 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -80,6 +80,28 @@ enum avic_ipi_failure_cause {
 	AVIC_IPI_FAILURE_INVALID_BACKING_PAGE,
 };
 
+
+static void __avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
+{
+	if (is_run)
+		avic_vcpu_load(vcpu, vcpu->cpu);
+	else
+		avic_vcpu_put(vcpu);
+}
+
+/*
+ * This function is called during VCPU halt/unhalt.
+ */
+static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	svm->avic_is_running = is_run;
+
+	if (kvm_vcpu_apicv_active(vcpu))
+		__avic_set_running(vcpu, is_run);
+}
+
 /* Note:
  * This function is called from IOMMU driver to notify
  * SVM to schedule in a particular vCPU of a particular VM.
@@ -651,6 +673,7 @@ void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 	}
 	vmcb_mark_dirty(vmcb, VMCB_AVIC);
 
+	__avic_set_running(vcpu, activated);
 	svm_set_pi_irte_mode(vcpu, activated);
 }
 
@@ -940,9 +963,6 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	int h_physical_id = kvm_cpu_get_apicid(cpu);
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	if (!kvm_vcpu_apicv_active(vcpu))
-		return;
-
 	/*
 	 * Since the host physical APIC id is 8 bits,
 	 * we can support host APIC ID upto 255.
@@ -970,9 +990,6 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
 	u64 entry;
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	if (!kvm_vcpu_apicv_active(vcpu))
-		return;
-
 	entry = READ_ONCE(*(svm->avic_physical_id_cache));
 	if (entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK)
 		avic_update_iommu_vcpu_affinity(vcpu, -1, 0);
@@ -981,20 +998,6 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
 	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
 }
 
-/*
- * This function is called during VCPU halt/unhalt.
- */
-static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
-{
-	struct vcpu_svm *svm = to_svm(vcpu);
-
-	svm->avic_is_running = is_run;
-	if (is_run)
-		avic_vcpu_load(vcpu, vcpu->cpu);
-	else
-		avic_vcpu_put(vcpu);
-}
-
 void svm_vcpu_blocking(struct kvm_vcpu *vcpu)
 {
 	avic_set_running(vcpu, false);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c8827de49c75..61b5faba36cf 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1483,12 +1483,16 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		sd->current_vmcb = svm->vmcb;
 		indirect_branch_prediction_barrier();
 	}
-	avic_vcpu_load(vcpu, cpu);
+
+	if (kvm_vcpu_apicv_active(vcpu))
+		avic_vcpu_load(vcpu, cpu);
 }
 
 static void svm_vcpu_put(struct kvm_vcpu *vcpu)
 {
-	avic_vcpu_put(vcpu);
+	if (kvm_vcpu_apicv_active(vcpu))
+		avic_vcpu_put(vcpu);
+
 	svm_prepare_host_switch(vcpu);
 
 	++vcpu->stat.host_state_reload;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9d2e4594c4eb..67bea0809636 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9239,12 +9239,18 @@ void kvm_make_scan_ioapic_request(struct kvm *kvm)
 
 void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
 {
+	bool activate;
+
 	if (!lapic_in_kernel(vcpu))
 		return;
 
 	mutex_lock(&vcpu->kvm->arch.apicv_update_lock);
 
-	vcpu->arch.apicv_active = kvm_apicv_activated(vcpu->kvm);
+	activate = kvm_apicv_activated(vcpu->kvm);
+	if (vcpu->arch.apicv_active == activate)
+		goto out;
+
+	vcpu->arch.apicv_active = activate;
 	kvm_apic_update_apicv(vcpu);
 	static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);
 
@@ -9257,6 +9263,7 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
 	if (!vcpu->arch.apicv_active)
 		kvm_make_request(KVM_REQ_EVENT, vcpu);
 
+out:
 	mutex_unlock(&vcpu->kvm->arch.apicv_update_lock);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_update_apicv);
-- 
2.26.3