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Date: Thu, 6 Dec 2012 13:53:41 +0100
From: Stefan Hajnoczi <stefanha@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring
	code
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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@nongnu.org, Blue Swirl <blauwirbel@gmail.com>, khoa@us.ibm.com, Paolo Bonzini <pbonzini@redhat.com>, asias@redhat.com

On Thu, Dec 06, 2012 at 01:22:29PM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 05, 2012 at 09:47:03PM +0100, Stefan Hajnoczi wrote:
> > The virtio-blk-data-plane cannot access memory using the usual QEMU
> > functions since it executes outside the global mutex and the memory APIs
> > are this time are not thread-safe.
> > 
> > This patch introduces a virtqueue module based on the kernel's vhost
> > vring code.  The trick is that we map guest memory ahead of time and
> > access it cheaply outside the global mutex.
> 
> Question: can virtio.c be reworked to use vring.c instead?
> The cost of keeping an extra memory listener around seems negligeable.
> The only issue I see is around dirty tracking for used ring writes.
> Maybe we could add a callback for this?

virtio.c and dataplane/vring.c will be unified but I think it's beyond
the scope of this series.  This is the thread-safe memory API
refactoring we discussed.

Stefan