KVM: Use kmem cache for allocating vcpus

Avi wants the allocations of vcpus centralized again.  The easiest way
is to add a "size" arg to kvm_init_arch, and expose the thus-prepared
cache to the modules.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/kvm.h

@@ -141,6 +141,7 @@ struct kvm_mmu_page {
 };
 
 struct kvm_vcpu;
+extern struct kmem_cache *kvm_vcpu_cache;
 
 /*
  * x86 supports 3 paging modes (4-level 64-bit, 3-level 64-bit, and 2-level
@@ -483,7 +484,8 @@ extern struct kvm_arch_ops *kvm_arch_ops;
 int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id);
 void kvm_vcpu_uninit(struct kvm_vcpu *vcpu);
 
-int kvm_init_arch(struct kvm_arch_ops *ops, struct module *module);
+int kvm_init_arch(struct kvm_arch_ops *ops, unsigned int vcpu_size,
+		  struct module *module);
 void kvm_exit_arch(void);
 
 int kvm_mmu_module_init(void);

drivers/kvm/kvm_main.c

@@ -53,6 +53,8 @@ static LIST_HEAD(vm_list);
 static cpumask_t cpus_hardware_enabled;
 
 struct kvm_arch_ops *kvm_arch_ops;
+struct kmem_cache *kvm_vcpu_cache;
+EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
 
 static __read_mostly struct preempt_ops kvm_preempt_ops;
 
@@ -3104,7 +3106,8 @@ static void kvm_sched_out(struct preempt_notifier *pn,
 	kvm_arch_ops->vcpu_put(vcpu);
 }
 
-int kvm_init_arch(struct kvm_arch_ops *ops, struct module *module)
+int kvm_init_arch(struct kvm_arch_ops *ops, unsigned int vcpu_size,
+		  struct module *module)
 {
 	int r;
 
@@ -3142,6 +3145,14 @@ int kvm_init_arch(struct kvm_arch_ops *ops, struct module *module)
 	if (r)
 		goto out_free_3;
 
+	/* A kmem cache lets us meet the alignment requirements of fx_save. */
+	kvm_vcpu_cache = kmem_cache_create("kvm_vcpu", vcpu_size,
+					   __alignof__(struct kvm_vcpu), 0, 0);
+	if (!kvm_vcpu_cache) {
+		r = -ENOMEM;
+		goto out_free_4;
+	}
+
 	kvm_chardev_ops.owner = module;
 
 	r = misc_register(&kvm_dev);
@@ -3156,6 +3167,8 @@ int kvm_init_arch(struct kvm_arch_ops *ops, struct module *module)
 	return r;
 
 out_free:
+	kmem_cache_destroy(kvm_vcpu_cache);
+out_free_4:
 	sysdev_unregister(&kvm_sysdev);
 out_free_3:
 	sysdev_class_unregister(&kvm_sysdev_class);
@@ -3173,6 +3186,7 @@ out:
 void kvm_exit_arch(void)
 {
 	misc_deregister(&kvm_dev);
+	kmem_cache_destroy(kvm_vcpu_cache);
 	sysdev_unregister(&kvm_sysdev);
 	sysdev_class_unregister(&kvm_sysdev_class);
 	unregister_reboot_notifier(&kvm_reboot_notifier);

drivers/kvm/svm.c

@@ -577,7 +577,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
 	struct page *page;
 	int err;
 
-	svm = kzalloc(sizeof *svm, GFP_KERNEL);
+	svm = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
 	if (!svm) {
 		err = -ENOMEM;
 		goto out;
@@ -1849,7 +1849,8 @@ static struct kvm_arch_ops svm_arch_ops = {
 
 static int __init svm_init(void)
 {
-	return kvm_init_arch(&svm_arch_ops, THIS_MODULE);
+	return kvm_init_arch(&svm_arch_ops, sizeof(struct vcpu_svm),
+			      THIS_MODULE);
 }
 
 static void __exit svm_exit(void)

drivers/kvm/vmx.c

@@ -2365,7 +2365,7 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
 static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 {
 	int err;
-	struct vcpu_vmx *vmx = kzalloc(sizeof(*vmx), GFP_KERNEL);
+	struct vcpu_vmx *vmx = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
 	int cpu;
 
 	if (!vmx)
@@ -2490,7 +2490,7 @@ static int __init vmx_init(void)
 	memset(iova, 0xff, PAGE_SIZE);
 	kunmap(vmx_io_bitmap_b);
 
-	r = kvm_init_arch(&vmx_arch_ops, THIS_MODULE);
+	r = kvm_init_arch(&vmx_arch_ops, sizeof(struct vcpu_vmx), THIS_MODULE);
 	if (r)
 		goto out1;