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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 16 Mar 2016 12:54:32 +0100
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Subject: Re: [Qemu-devel] [PATCH 0/4] Tweaks around virtio-blk start/stop
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To: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, qemu-block@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, Christian Borntraeger <borntraeger@de.ibm.com>, tubo@linux.vnet.ibm.com, Stefan Hajnoczi <stefanha@redhat.com>



On 16/03/2016 12:52, Cornelia Huck wrote:
> > Hm... I copied these semantics from virtio-pci, and they still seem to
> > be the same. I wonder why we never saw this on virtio-pci?
> > 
> > > In dataplane, instead, all calls to
> > > virtio_queue_set_host_notifier_fd_handler and
> > > virtio_queue_aio_set_host_notifier_handler should have assign=true.  The
> > > ioeventfd is just being moved from one aiocontext to another.
> > 
> > How can a transport know where they are called from?
> 
> Hm^2... I looked at virtio-scsi dataplane, and I noticed that it
> acquires the aio context prior to calling ->set_host_notifiers(). Does
> virtio-blk dataplane need to do this as well, or is virtio-scsi
> dataplane wrong/different?

I cannot really answer, but my plan was to solve this bug and then
ensure that virtio-scsi dataplane does exactly the same thing...  I
would ignore virtio-scsi dataplane for now.

Paolo