KVM: Split vcpu creation to avoid vcpu_load() before preemption setup

Split kvm_arch_vcpu_create() into kvm_arch_vcpu_create() and
kvm_arch_vcpu_setup(), enabling preemption notification between the two.
This mean that we can now do vcpu_load() within kvm_arch_vcpu_setup().

Signed-off-by: Avi Kivity <avi@qumranet.com>

3 files changed, 12 insertions, 9 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 49094a221f6a..b65f5dee4b1b 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -466,6 +466,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu);
 struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id);
+int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu);
 
 int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu);
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 9dd6ad3c6c7b..7939b5c9a4b4 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -769,6 +769,10 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n)
 
         preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
 
+        r = kvm_arch_vcpu_setup(vcpu);
+        if (r)
+                goto vcpu_destroy;
+
         mutex_lock(&kvm->lock);
         if (kvm->vcpus[n]) {
                 r = -EEXIST;
diff --git a/drivers/kvm/x86.c b/drivers/kvm/x86.c
index 6abb2ed1a908..b482b6a8a828 100644
--- a/drivers/kvm/x86.c
+++ b/drivers/kvm/x86.c
@@ -2478,13 +2478,12 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
 struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
                                                 unsigned int id)
 {
-        int r;
-        struct kvm_vcpu *vcpu = kvm_x86_ops->vcpu_create(kvm, id);
+        return kvm_x86_ops->vcpu_create(kvm, id);
+}
 
-        if (IS_ERR(vcpu)) {
-                r = -ENOMEM;
-                goto fail;
-        }
+int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
+{
+        int r;
 
         /* We do fxsave: this must be aligned. */
         BUG_ON((unsigned long)&vcpu->host_fx_image & 0xF);
@@ -2497,11 +2496,10 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
         if (r < 0)
                 goto free_vcpu;
 
-        return vcpu;
+        return 0;
 free_vcpu:
         kvm_x86_ops->vcpu_free(vcpu);
-fail:
-        return ERR_PTR(r);
+        return r;
 }
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)