KVM: remove kvm_vcpu_compatible

The new created_vcpus field makes it possible to avoid the race between
irqchip and VCPU creation in a much nicer way; just check under kvm->lock
whether a VCPU has already been created.

We can then remove KVM_APIC_ARCHITECTURE too, because at this point the
symbol is only governing the default definition of kvm_vcpu_compatible.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/Kconfig

@@ -32,7 +32,6 @@ config KVM
 	select HAVE_KVM_IRQ_BYPASS
 	select HAVE_KVM_IRQ_ROUTING
 	select HAVE_KVM_EVENTFD
-	select KVM_APIC_ARCHITECTURE
 	select KVM_ASYNC_PF
 	select USER_RETURN_NOTIFIER
 	select KVM_MMIO

arch/x86/kvm/x86.c

@@ -3774,7 +3774,7 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		r = -EEXIST;
 		if (irqchip_in_kernel(kvm))
 			goto split_irqchip_unlock;
-		if (atomic_read(&kvm->online_vcpus))
+		if (kvm->created_vcpus)
 			goto split_irqchip_unlock;
 		r = kvm_setup_empty_irq_routing(kvm);
 		if (r)
@@ -3839,7 +3839,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		if (kvm->arch.vpic)
 			goto create_irqchip_unlock;
 		r = -EINVAL;
-		if (atomic_read(&kvm->online_vcpus))
+		if (kvm->created_vcpus)
 			goto create_irqchip_unlock;
 		r = -ENOMEM;
 		vpic = kvm_create_pic(kvm);
@@ -3995,7 +3995,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	case KVM_SET_BOOT_CPU_ID:
 		r = 0;
 		mutex_lock(&kvm->lock);
-		if (atomic_read(&kvm->online_vcpus) != 0)
+		if (kvm->created_vcpus)
 			r = -EBUSY;
 		else
 			kvm->arch.bsp_vcpu_id = arg;
@@ -7639,11 +7639,6 @@ 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)
-{
-	return irqchip_in_kernel(vcpu->kvm) == lapic_in_kernel(vcpu);
-}
-
 struct static_key kvm_no_apic_vcpu __read_mostly;
 EXPORT_SYMBOL_GPL(kvm_no_apic_vcpu);
 

include/linux/kvm_host.h

@@ -1105,12 +1105,6 @@ static inline int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 
 #endif /* CONFIG_HAVE_KVM_EVENTFD */
 
-#ifdef CONFIG_KVM_APIC_ARCHITECTURE
-bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
-#else
-static inline bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu) { return true; }
-#endif
-
 static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
 {
 	/*

virt/kvm/Kconfig

@@ -16,9 +16,6 @@ config HAVE_KVM_EVENTFD
        bool
        select EVENTFD
 
-config KVM_APIC_ARCHITECTURE
-       bool
-
 config KVM_MMIO
        bool
 

virt/kvm/kvm_main.c

@@ -2368,10 +2368,6 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 		goto vcpu_destroy;
 
 	mutex_lock(&kvm->lock);
-	if (!kvm_vcpu_compatible(vcpu)) {
-		r = -EINVAL;
-		goto unlock_vcpu_destroy;
-	}
 	if (kvm_get_vcpu_by_id(kvm, id)) {
 		r = -EEXIST;
 		goto unlock_vcpu_destroy;