linux-kernel - [PATCH v3 10/16] svm: Disable AVIC when launching guest with SVM support

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Message-ID: <1568401242-260374-11-git-send-email-suravee.suthikulpanit@amd.com>
Date:   Fri, 13 Sep 2019 19:01:02 +0000
From:   "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "graf@...zon.com" <graf@...zon.com>,
        "jschoenh@...zon.de" <jschoenh@...zon.de>,
        "karahmed@...zon.de" <karahmed@...zon.de>,
        "rimasluk@...zon.com" <rimasluk@...zon.com>,
        "Grimm, Jon" <Jon.Grimm@....com>,
        "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>
Subject: [PATCH v3 10/16] svm: Disable AVIC when launching guest with SVM
 support

Since AVIC does not currently work w/ nested virtualization, disable 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@...zon.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/svm.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a01bc6a..e02ee1a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6029,6 +6029,16 @@ 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)) {
+		vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+		kvm_make_apicv_deactivate_request(vcpu, true);
+		srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
+	}
 }
 
 static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
-- 
1.8.3.1