Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server

From: Michael S. Tsirkin
Date: Wed Nov 04 2009 - 08:12:05 EST

On Wed, Nov 04, 2009 at 01:59:57PM +0100, Andi Kleen wrote:
> > Fine?
> I cannot say -- are there paths that could drop the device beforehand?

Do you mean drop the mm reference?

> (as in do you hold a reference to it?)

By design I think I always have a reference to mm before I use it.

This works like this:
ioctl SET_OWNER - calls get_task_mm, I think this gets a reference to mm
ioctl SET_BACKEND - checks that SET_OWNER was run, starts virtqueue
ioctl RESET_OWNER - stops virtqueues, drops the reference to mm
file close - stops virtqueues, if we still have it then drops mm

This is why I think I can call use_mm/unuse_mm while virtqueue is running,
Makes sense?

> -Andi
> --
> ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at