[PATCH v4 11/17] svm: Deactivate AVIC when launching guest with nested SVM support

[Suthikulpanit, Suravee]

Since AVIC does not currently work w/ nested virtualization,
deactivate AVIC for the guest if setting CPUID Fn80000001_ECX[SVM]
(i.e. indicate support for SVM, which is needed for nested virtualization).

Suggested-by: Alexander Graf <graf@xxxxxxxxxx>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/svm.c              | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a6475fd..55d6476 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -856,6 +856,7 @@ enum kvm_irqchip_mode {
 
 #define APICV_DEACT_BIT_DISABLE    0
 #define APICV_DEACT_BIT_HYPERV     1
+#define APICV_DEACT_BIT_NESTED     2
 
 struct kvm_arch {
 	unsigned long n_used_mmu_pages;
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5b90458..7f59b1a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5984,6 +5984,14 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
 		return;
 
 	guest_cpuid_clear(vcpu, X86_FEATURE_X2APIC);
+
+	/*
+	 * Currently, AVIC does not work with nested virtualization.
+	 * So, we disable AVIC when cpuid for SVM is set in the L1 guest.
+	 */
+	if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM))
+		kvm_request_apicv_update(vcpu->kvm, false,
+					 APICV_DEACT_BIT_NESTED);
 }
 
 static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
-- 
1.8.3.1