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 <namit@cs.technion.ac.il>
Message-Id: <1427933438-12782-3-git-send-email-namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 11a0af113f275f7ef35dbec4581b3e748a37e853..4a6e58a967f7bef87788debf89eee0a7a7e37da0 100644 (file)
--- 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
index 155534c0f5e8ad3c0f003c0b608ce0151f1cf1eb..ce741b8650f6ece694fb47e1750d153291a1803f 100644 (file)
--- 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
index ddce07e8bef849bafb88e4229c36d4b462135d83..8c14d6a455b00ed446c7b97b6bdd5288214a728c 100644 (file)
--- 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
index a578629acb42121eab42da7a2460df3f6b8fa944..f7a78c62ab870bb4911fa1b377be9c4095019ea9 100644 (file)
--- 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
index 27bd53b690803170f53c31e485a23c43496ffdfb..82af5d0b996e7fb29edd029379f2ab9238a1b2a2 100644 (file)
--- 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