Re: [Qemu-devel] [PATCHv3 4/6] virtio-net: stop/start bh when appropriate

[Kevin Wolf]

Am 01.12.2010 06:59, schrieb Michael S. Tsirkin:
> On Wed, Dec 01, 2010 at 01:45:09PM +0800, Jason Wang wrote:
>> Michael S. Tsirkin writes:
>>  > Avoid sending out packets, and modifying
>>  > device state, when VM is stopped.
>>  > Add assert statements to verify this does not happen.
>>  > 
>>  > Avoid scheduling bh when vhost-net is started.
>>  > 
>>  > Stop bh when driver disabled bus mastering
>>  > (we must not access memory after this).
>>  > 
>>  > Signed-off-by: Michael S. Tsirkin <address@hidden>
>>  > 
>>
>> There's no need to disable it bh we call qemu_aio_flush() after
>> vm_state_notify() in do_vm_stop().
> 
> Yes, but bh can resubmit itself, so flush is not enough.
> Note that vm stop is not the only reason to avoid
> running bh: when vhost-net is enabled we should avoid it too.
> Makes sense?

If I understand correctly, qemu_aio_flush() is supposed to also execute
the resubmitted BH, so that you really end up with an empty BH list.

Kevin