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Date: Thu, 29 Nov 2012 15:48:04 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20121129144804.GC14196@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 00/11] virtio: virtio-blk data plane
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel <qemu-devel@nongnu.org>, Blue Swirl <blauwirbel@gmail.com>, Khoa Huynh <khoa@us.ibm.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Asias He <asias@redhat.com>

On Thu, Nov 29, 2012 at 04:09:28PM +0200, Michael S. Tsirkin wrote:
> On Thu, Nov 29, 2012 at 10:18:59AM +0100, Stefan Hajnoczi wrote:
> > Michael, Paolo: Are you happy with v4?
> 
> Looks pretty clean by itself. I sent some comments but they can be
> addressed later.  What worries me most is the code duplication with
> regular virtio.
> 
> I see two ways to reduce the maintainance somewhat
> - split out ring handling code in virtio-blk
>   to a separate file to make it more obvious which part
>   is inactive when data plane runs.
> - share ring processing code with virtio/virtio-blk
>   (e.g. use callbacks)
> 
> Was any thought given to implementing one of these two
> approaches? 

Yes, your option #2 is where I'd like to move once threaded memory
dispatch is working.  I hope we can run virtio.c code in a thread
outside the global mutex soon.  That way we can kill
hw/dataplane/vring.[ch].

Ping Fan Liu has been working on the memory API and device emulation
stuff that we need in order to eventually use virtio.c outside the
global mutex.

Stefan