Re: [Xen-devel] [PATCH] libxl: prefer qdisk over blktap when choosing disk backend

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Aug 28, 2013 at 03:16:23PM +0200, Fabio Fantoni wrote:
> Il 28/08/2013 15:04, Ian Jackson ha scritto:
> >Fabio Fantoni writes ("Re: [Xen-devel] [PATCH] libxl: prefer qdisk over 
> >blktap when choosing disk backend"):
> >>I think is good prefer qdisk also for significant performance increase
> >>in comparison with blktap2.
> >Thanks, that's useful information.  That, and what George said, have
> >convinced me this is the right change.
> >
> >Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> 
> What about qemu traditional with this patch?
> I haven't tested qdisk with qemu traditional but unfortunately
> qemu-trad. is still widely used and therefore you have to be sure
> that does not cause problems.

Ah, now I get your question.

> I asked about because devices parts seem the same with both qemu but
> I not sure about it.

We've already switched to qemu-upstream in 4.3. And this patch is not
backport material so old system would just work fine IMHO.

The only risk of breakage is: users have device_model_version set to
qemu-trad and run blktap kernel with Xen pre-4.3, then upgrade to Xen
post-4.3 (with this patch). I've tested that, and qemu-trad runs fine
for me -- at least it boots and dd works well.

Wei.

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