Re: [PATCH v4 13/26] KVM: Add arch hook when VM is added/deleted

[Chao Gao]

On Thu, Sep 08, 2022 at 04:25:29PM -0700, isaku.yamahata@xxxxxxxxx wrote:
>+__weak int kvm_arch_post_init_vm(struct kvm *kvm)

int __weak

>+{
>+	return 0;
>+}
>+
> /*
>  * Called after the VM is otherwise initialized, but just before adding it to
>  * the vm_list.
>  */
>-__weak int kvm_arch_post_init_vm(struct kvm *kvm)
>+__weak int kvm_arch_add_vm(struct kvm *kvm, int usage_count)
>+{
>+	return kvm_arch_post_init_vm(kvm);
>+}
>+
>+__weak int kvm_arch_del_vm(int usage_count)

ditto

>+static void kvm_del_vm(void)
>+{
>+	cpus_read_lock();
>+	mutex_lock(&kvm_lock);
>+	kvm_arch_del_vm(kvm_usage_count);
>+	mutex_unlock(&kvm_lock);
>+	cpus_read_unlock();

kvm_arch_del_vm() is an empty function now. I don't understand why
cpus_read_lock() is needed. Maybe add the lock when you fill up
kvm_arch_del_vm().