linux-kernel - [PART1 RFC v4 09/11] svm: Do not expose x2APIC when enable AVIC

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Date:	Thu, 7 Apr 2016 03:20:30 -0500
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	<pbonzini@...hat.com>, <rkrcmar@...hat.com>, <joro@...tes.org>,
	<bp@...en8.de>, <gleb@...nel.org>, <alex.williamson@...hat.com>
CC:	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<wei@...hat.com>, <sherry.hurwitz@....com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PART1 RFC v4 09/11] svm: Do not expose x2APIC when enable AVIC

From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>

Since AVIC only virtualizes xAPIC hardware for the guest, this patch
disable x2APIC support in guest CPUID.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/svm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 13fba3b..74b0751 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4560,14 +4560,26 @@ static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
 static void svm_cpuid_update(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	struct kvm_cpuid_entry2 *entry;
 
 	/* Update nrips enabled cache */
 	svm->nrips_enabled = !!guest_cpuid_has_nrips(&svm->vcpu);
+
+	if (!svm_vcpu_avic_enabled(svm))
+		return;
+
+	entry = kvm_find_cpuid_entry(vcpu, 0x1, 0);
+	if (entry->function == 1)
+		entry->ecx &= ~bit(X86_FEATURE_X2APIC);
 }
 
 static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
 {
 	switch (func) {
+	case 0x00000001:
+		if (avic)
+			entry->ecx &= ~bit(X86_FEATURE_X2APIC);
+		break;
 	case 0x80000001:
 		if (nested)
 			entry->ecx |= (1 << 2); /* Set SVM bit */
-- 
1.9.1