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>

4 files changed, 3 insertions, 5 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 11a0af113f27..4a6e58a967f7 100644
--- 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 155534c0f5e8..ce741b8650f6 100644
--- 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 ddce07e8bef8..8c14d6a455b0 100644
--- 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 a578629acb42..f7a78c62ab87 100644
--- 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;