Re: [Xen-devel] [Qemu-devel] Question about xen disk unplug support for ahci missed in qemu

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 19/10/2015 12:18, Stefano Stabellini ha scritto:
> On Fri, 16 Oct 2015, John Snow wrote:
> > On 10/13/2015 01:10 PM, Stefano Stabellini wrote:
> > > On Tue, 13 Oct 2015, John Snow wrote:
> > > > On 10/13/2015 11:55 AM, Fabio Fantoni wrote:
> > > > > I added ahci disk support in libxl and using it for week seems that was
> > > > > ok, after a reply of Stefano Stabellini seems that xen disk unplug
> > > > > support only ide disks:
> > > > > http://git.qemu.org/?p=qemu.git;a=commitdiff;h=679f4f8b178e7c66fbc2f39c905374ee8663d5d8
> > > > >
> > > > > Today Paul Durrant told me that even if pv disk is ok also with ahci and
> > > > > the emulated one is offline can be a risk:
> > > > > http://lists.xenproject.org/archives/html/win-pv-devel/2015-10/msg00021.html
> > > > >
> > > > >
> > > > > I tried to take a fast look in qemu code but I not understand the needed
> > > > > thing for add the xen disk unplug support also for ahci, can someone do
> > > > > it or tell me useful information for do it please?
> > > > >
> > > > > Thanks for any reply and sorry for my bad english.
> > > > I'm not entirely sure what features you need AHCI to support in order
> > > > for Xen to be happy.
> > > >
> > > > I'd guess hotplugging, but where I get confused is that IDE disks don't
> > > > support hotplugging either, so I guess I'm not sure sure what you need.
> > > >
> > > > Stefano, can you help bridge my Xen knowledge gap?
> > >   
> > > Hi John,
> > > we need something like hw/i386/xen/xen_platform.c:unplug_disks but that
> > > can unplug AHCI disk. And by unplug, I mean "make disappear" like
> > > pci_piix3_xen_ide_unplug does for ide.
> > I'm trying to follow this discussion as best as I am able, but my lack
> > of experience with Xen prevents me from really participating in a
> > meaningful way.
> >
> > (I see that Laszlo is still discussing some CD-ROM issues with Fabio
> > which may be of interest to me...)
> >
> > At any rate, I won't be authoring any Xen-specific hacks to the AHCI
> > device, but I do have plans to implement hot-plugging emulation as per
> > the AHCI spec. Perhaps this is sufficient for the Xen layer, but someone
> > else will need to author the appropriate glue code.
> >
> > If "real" hot-plugging is not sufficient, we'll need to discuss further,
> > preferably over some RFC patches.
> That's fine. AHCI hot-plugging would go a long way and once we have
> that, the rest is easy.
>
> Thanks,
>
> Stefano
Thanks for any improvement you will do.
About AHCI hotplugging will remove bad thing of actual "xen unplug" in 
seabios/ovmf but not the hybrid pv solution right?
Doing without hybrid like what I tried you told me with ovmf probably is 
better solution after solving other bugs but probably someone don't want 
plain remove it.
About empty cdrom not working in ovmf but needed by xl 
cd-insert/cd-eject I suppose that is easly reproducible, I had it in any 
case I tested.
If not and more details are needed tell me and I'll rebuild and test 
following Lazslo instructions.
Thanks for any reply and sorry for my bad english.

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