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From:   "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>
CC:     "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "rkrcmar@redhat.com" <rkrcmar@redhat.com>,
        "joro@8bytes.org" <joro@8bytes.org>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>,
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        "karahmed@amazon.de" <karahmed@amazon.de>,
        "rimasluk@amazon.com" <rimasluk@amazon.com>,
        "Grimm, Jon" <Jon.Grimm@amd.com>,
        "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>
Subject: [PATCH v4 11/17] svm: Deactivate AVIC when launching guest with
 nested SVM support
Thread-Topic: [PATCH v4 11/17] svm: Deactivate AVIC when launching guest with
 nested SVM support
Thread-Index: AQHVkQWE5V+cC6Hpf0OQw3ASVtcOMQ==
Date:   Fri, 1 Nov 2019 22:41:35 +0000
Message-ID: <1572648072-84536-12-git-send-email-suravee.suthikulpanit@amd.com>
References: <1572648072-84536-1-git-send-email-suravee.suthikulpanit@amd.com>
In-Reply-To: <1572648072-84536-1-git-send-email-suravee.suthikulpanit@amd.com>
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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@amazon.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 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_hos=
t.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 {
=20
 #define APICV_DEACT_BIT_DISABLE    0
 #define APICV_DEACT_BIT_HYPERV     1
+#define APICV_DEACT_BIT_NESTED     2
=20
 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;
=20
 	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);
 }
=20
 static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *ent=
ry)
--=20
1.8.3.1