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Date: Fri, 03 Dec 2010 09:40:50 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCHv3 4/6] virtio-net: stop/start bh
	when	appropriate
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>, mtosatti@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com

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 <mst@redhat.com>
>>  > 
>>
>> 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