linux-kernel - [RFC PATCH 06/13] KVM: SVM: Add logic to determine x2APIC mode

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Date:   Sun, 20 Feb 2022 20:19:15 -0600
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
CC:     <pbonzini@...hat.com>, <seanjc@...gle.com>, <joro@...tes.org>,
        <jon.grimm@....com>, <wei.huang2@....com>, <terry.bowman@....com>,
        "Suravee Suthikulpanit" <suravee.suthikulpanit@....com>
Subject: [RFC PATCH 06/13] KVM: SVM: Add logic to determine x2APIC mode

Introduce avic_update_vapic_bar(), which checks the x2APIC enable bit
of the APIC Base register and update the new struct vcpu_svm.x2apic_enabled
to keep track of current APIC mode of each vCPU,

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/svm/avic.c | 13 +++++++++++++
 arch/x86/kvm/svm/svm.c  |  4 ++++
 arch/x86/kvm/svm/svm.h  |  2 ++
 3 files changed, 19 insertions(+)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 1999076966fd..60f30e48d816 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -609,6 +609,19 @@ void avic_post_state_restore(struct kvm_vcpu *vcpu)
 	avic_handle_ldr_update(vcpu);
 }
 
+void avic_update_vapic_bar(struct vcpu_svm *svm, u64 data)
+{
+	svm->vmcb->control.avic_vapic_bar = data & VMCB_AVIC_APIC_BAR_MASK;
+
+	/* Set x2APIC mode bit if guest enable x2apic mode. */
+	svm->x2apic_enabled = (avic_mode == AVIC_MODE_X2 &&
+			       kvm_apic_mode(data) == LAPIC_MODE_X2APIC);
+	pr_debug("vcpu_id:%d switch to %s\n", svm->vcpu.vcpu_id,
+		 svm->x2apic_enabled ? "x2APIC" : "xAPIC");
+	vmcb_mark_dirty(svm->vmcb, VMCB_AVIC);
+	kvm_vcpu_update_apicv(&svm->vcpu);
+}
+
 void svm_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
 {
 	return;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 3687026f2859..4e6dc1feeac7 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2867,6 +2867,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		svm->msr_decfg = data;
 		break;
 	}
+	case MSR_IA32_APICBASE:
+		if (kvm_vcpu_apicv_active(vcpu))
+			avic_update_vapic_bar(to_svm(vcpu), data);
+		fallthrough;
 	default:
 		return kvm_set_msr_common(vcpu, msr);
 	}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 1a0bf6b853df..bfbebb933da2 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -225,6 +225,7 @@ struct vcpu_svm {
 	u32 dfr_reg;
 	struct page *avic_backing_page;
 	u64 *avic_physical_id_cache;
+	bool x2apic_enabled;
 
 	/*
 	 * Per-vcpu list of struct amd_svm_iommu_ir:
@@ -566,6 +567,7 @@ void avic_init_vmcb(struct vcpu_svm *svm);
 int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu);
 int avic_unaccelerated_access_interception(struct kvm_vcpu *vcpu);
 int avic_init_vcpu(struct vcpu_svm *svm);
+void avic_update_vapic_bar(struct vcpu_svm *svm, u64 data);
 void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
 void avic_vcpu_put(struct kvm_vcpu *vcpu);
 void avic_post_state_restore(struct kvm_vcpu *vcpu);
-- 
2.25.1