linux-kernel - [RFCv2 PATCH 07/12] KVM: SVM: Introduce helper function kvm_get_apic

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Date:   Tue, 8 Mar 2022 10:39:21 -0600
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
CC:     <pbonzini@...hat.com>, <mlevitsk@...hat.com>, <seanjc@...gle.com>,
        <joro@...tes.org>, <jon.grimm@....com>, <wei.huang2@....com>,
        <terry.bowman@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [RFCv2 PATCH 07/12] KVM: SVM: Introduce helper function kvm_get_apic_id

This function returns the currently programmed guest physical
APIC ID of a vCPU in both xAPIC and x2APIC modes.

Suggested-by: Maxim Levitsky <mlevitsk@...hat.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/lapic.c    | 23 +++++++++++++++++++++++
 arch/x86/kvm/lapic.h    |  5 +----
 arch/x86/kvm/svm/avic.c | 21 +++++++++++++++++----
 3 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 03d1b6325eb8..73a1e650a294 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -106,11 +106,34 @@ static inline int apic_enabled(struct kvm_lapic *apic)
 	(LVT_MASK | APIC_MODE_MASK | APIC_INPUT_POLARITY | \
 	 APIC_LVT_REMOTE_IRR | APIC_LVT_LEVEL_TRIGGER)
 
+static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
+{
+	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
+}
+
 static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
 {
 	return apic->vcpu->vcpu_id;
 }
 
+int kvm_get_apic_id(struct kvm_vcpu *vcpu, u32 *id)
+{
+	if (!id)
+		return -EINVAL;
+
+	if (!apic_x2apic_mode(vcpu->arch.apic)) {
+		/* For xAPIC, APIC ID cannot be larger than 254. */
+		if (vcpu->vcpu_id >= APIC_BROADCAST)
+			return -EINVAL;
+
+		*id = kvm_xapic_id(vcpu->arch.apic);
+	} else {
+		*id = kvm_x2apic_id(vcpu->arch.apic);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_get_apic_id);
+
 static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu)
 {
 	return pi_inject_timer && kvm_vcpu_apicv_active(vcpu);
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 2b44e533fc8d..2b9463da1528 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -254,9 +254,6 @@ static inline enum lapic_mode kvm_apic_mode(u64 apic_base)
 	return apic_base & (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE);
 }
 
-static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
-{
-	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
-}
+int kvm_get_apic_id(struct kvm_vcpu *vcpu, u32 *id);
 
 #endif
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 4d7a8743196e..7e5a39a8e698 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -441,14 +441,21 @@ static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
 
 static int avic_handle_ldr_update(struct kvm_vcpu *vcpu)
 {
-	int ret = 0;
+	int ret;
 	struct vcpu_svm *svm = to_svm(vcpu);
 	u32 ldr = kvm_lapic_get_reg(vcpu->arch.apic, APIC_LDR);
-	u32 id = kvm_xapic_id(vcpu->arch.apic);
+	u32 id;
+
+	ret = kvm_get_apic_id(vcpu, &id);
+	if (ret)
+		return ret;
 
 	if (ldr == svm->ldr_reg)
 		return 0;
 
+	if (id == X2APIC_BROADCAST)
+		return -EINVAL;
+
 	avic_invalidate_logical_id_entry(vcpu);
 
 	if (ldr)
@@ -464,7 +471,12 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
 {
 	u64 *old, *new;
 	struct vcpu_svm *svm = to_svm(vcpu);
-	u32 id = kvm_xapic_id(vcpu->arch.apic);
+	u32 id;
+	int ret;
+
+	ret = kvm_get_apic_id(vcpu, &id);
+	if (ret)
+		return 1;
 
 	if (vcpu->vcpu_id == id)
 		return 0;
@@ -484,7 +496,8 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
 	 * APIC ID table entry if already setup the LDR.
 	 */
 	if (svm->ldr_reg)
-		avic_handle_ldr_update(vcpu);
+		if (avic_handle_ldr_update(vcpu))
+			return 1;
 
 	return 0;
 }
-- 
2.25.1