Re: [RFC][PATCH 1/5] [PATCH 1/5] kvm: register in task_struct

On 09/03/2018 04:10 PM, Nikita Leshenko wrote:

On September 2, 2018 5:21:15 AM, fengguang.wu@intel.com wrote:

quoted

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8b47507faab5..0c483720de8d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c

@@ -3892,6 +3892,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
 	if (type == KVM_EVENT_CREATE_VM) {
 		add_uevent_var(env, "EVENT=create");
 		kvm->userspace_pid = task_pid_nr(current);
+		current->kvm = kvm;

Is it OK to store `kvm` on the task_struct? What if the thread that
originally created the VM exits? From the documentation it seems
like a VM is associated with an address space and not a specific
thread, so maybe it should be stored on mm_struct?

Yes, ioctls accessing the kvm can happen from all threads.

From Documentation/virtual/kvm/api.txt:
   Only run VM ioctls from the same process (address space) that was used
   to create the VM.

-Nikita

quoted

 	} else if (type == KVM_EVENT_DESTROY_VM) {
 		add_uevent_var(env, "EVENT=destroy");
 	}
-- 
2.15.0