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

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 19/05/2015 12:40, Wei Liu ha scritto:
> 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.
This patch don't add q35 cipset support but only ich9 ahci disk 
controller in older and only cipset supported in xen.
Time ago I tried to add q35 support in xen but I had some problems I was 
unable to solves and nobody helped me.
Q35 have newer ich9 ahci disk controller as default, on older cipset 
must be added (done in this patch).
qemu, kvm ovmf already support q35, xen need changes at least in 
hvmloader (that I'm probably unable to do) and libxl (that I started 
time ago without good result), Add ahci support and switch all qemu 
parameters in libxl to new -device is a good start also for future q35 
support (are both part needed based on my old q35 tests on xen)
> > > > 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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