On Wed, Nov 04, 2009 at 03:08:28PM +0200, Michael S. Tsirkin wrote: > 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? No the reference to the device, which owns the mm for you. > > > (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, > safely. > Makes sense? Do you protect against another thread doing RESET_OWNER in parallel while RESET_OWNER runs? -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
