KVM: x86: BSP in MSR_IA32_APICBASE is writable

After reset, the CPU can change the BSP, which will be used upon INIT. Reset should return the BSP which QEMU asked for, and therefore handled accordingly. To quote: "If the MP protocol has completed and a BSP is chosen, subsequent INITs (either to a specific processor or system wide) do not cause the MP protocol to be repeated." [Intel SDM 8.4.2: MP Initialization Protocol Requirements and Restrictions] Signed-off-by: Nadav Amit <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
zhenyw · Apr 8, 2015 · 58d269d · 58d269d
1 parent 3b5a5ff
commit 58d269d
Show file tree

Hide file tree

Showing 5 changed files with 9 additions and 6 deletions.
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
@@ -1523,8 +1523,6 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
 		return;
 	}
 
-	if (!kvm_vcpu_is_bsp(apic->vcpu))
-		value &= ~MSR_IA32_APICBASE_BSP;
 	vcpu->arch.apic_base = value;
 
 	/* update jump label if enable bit changes */

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
@@ -1261,7 +1261,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
 
 	svm->vcpu.arch.apic_base = APIC_DEFAULT_PHYS_BASE |
 				   MSR_IA32_APICBASE_ENABLE;
-	if (kvm_vcpu_is_bsp(&svm->vcpu))
+	if (kvm_vcpu_is_reset_bsp(&svm->vcpu))
 		svm->vcpu.arch.apic_base |= MSR_IA32_APICBASE_BSP;
 
 	svm_init_osvw(&svm->vcpu);

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
@@ -4706,7 +4706,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 	vmx->vcpu.arch.regs[VCPU_REGS_RDX] = get_rdx_init_val();
 	kvm_set_cr8(&vmx->vcpu, 0);
 	apic_base_msr.data = APIC_DEFAULT_PHYS_BASE | MSR_IA32_APICBASE_ENABLE;
-	if (kvm_vcpu_is_bsp(&vmx->vcpu))
+	if (kvm_vcpu_is_reset_bsp(&vmx->vcpu))
 		apic_base_msr.data |= MSR_IA32_APICBASE_BSP;
 	apic_base_msr.host_initiated = true;
 	kvm_set_apic_base(&vmx->vcpu, &apic_base_msr);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
@@ -7269,7 +7269,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.pv.pv_unhalted = false;
 	vcpu->arch.emulate_ctxt.ops = &emulate_ops;
-	if (!irqchip_in_kernel(kvm) || kvm_vcpu_is_bsp(vcpu))
+	if (!irqchip_in_kernel(kvm) || kvm_vcpu_is_reset_bsp(vcpu))
 		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
 	else
 		vcpu->arch.mp_state = KVM_MP_STATE_UNINITIALIZED;

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
@@ -982,11 +982,16 @@ static inline int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 #endif /* CONFIG_HAVE_KVM_EVENTFD */
 
 #ifdef CONFIG_KVM_APIC_ARCHITECTURE
-static inline bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
+static inline bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu)
 {
 	return vcpu->kvm->bsp_vcpu_id == vcpu->vcpu_id;
 }
 
+static inline bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
+{
+	return (vcpu->arch.apic_base & MSR_IA32_APICBASE_BSP) != 0;
+}
+
 bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
 
 #else