Re: [Xen-devel] [PATCH v2][RFC] libxl: Add AHCI support for upstream qemu

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, May 18, 2015 at 07:22:01PM +0200, Fabio Fantoni wrote:
> Il 18/05/2015 17:53, Wei Liu ha scritto:
> >On Thu, May 14, 2015 at 01:11:13PM +0200, Fabio Fantoni wrote:
> >>Usage:
> >>ahci=0|1 (default=0)
> >>
> >>If enabled adds ich9 disk controller in ahci mode and uses it with
> >>upstream qemu to emulate disks instead of ide.
> >Is ICH9 available in our default setup?
> >
> >Why do we not always enable AHCI?
> 
> ahci seems require ich9 controller (default in q35 but not in older used by
> xen), I think that change it ide->ahci automatically for all cases may
> causes problems, probably in save/restore and more probably in windows <=7
> without pv where change ide<->ahci require a registry change for not have
> blue screen.
> 

I guess we now have a QEMU with Q35. But migrating from previous
previous versions will indeed need to be taken care of.

> >
> >>It doesn't support cdroms which still use ide (cdroms will use "-device
> >>ide-cd" as new qemu parameters)
> >>Ahci requires new qemu parameters but for now other emulated disks cases
> >>remains with old ones because automatic bus selection seems bugged in
> >>qemu using new parameters. (I'll retry)
> >>
> >Buggy as in? Have you reported to QEMU upstream?
> 
> Already reported long time ago in xen-devel and qemu-devel, the only reply
> from qemu-devel was to use fixed bus and is what I did in v2 of this patch.
> Can someone tell me if can be a problem fixed bus?
> 

I don't have enough knowledge on this. Maybe Anthony and Stefano have
more insight.

Wei.

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