Re: [Xen-devel] [PATCH v2 for 4.5] xen/arm: Add support for GICv3 for domU

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Nov 06, 2014 at 10:27:41AM +0000, Julien Grall wrote:
> 
> 
> On 06/11/2014 10:11, Jan Beulich wrote:
> >>>>On 06.11.14 at 10:45, <julien.grall@xxxxxxxxxx> wrote:
> >>Hi Jan,
> >>
> >>On 05/11/2014 17:15, Jan Beulich wrote:
> >>>>>>Julien Grall <julien.grall@xxxxxxxxxx> 11/04/14 6:27 PM >>>
> >>>>On 11/03/2014 04:39 PM, Konrad Rzeszutek Wilk wrote:
> >>>>>It also needs Acks from Daniel and Jan.
> >>>>
> >>>>This patch doesn't modify the x86 part. So I'm not sure if Jan ack is
> >>>>required. Would Ian C. ack be enough?
> >>>
> >>>Yes, it would.
> >>>
> >>>>Anyway, Jan do you have any objection on this patch?
> >>>
> >>>As said previously, I'm not particularly happy about it, but I also don't
> >>strongly
> >>>mind it going in in the current shape.
> >>
> >>May I ask what is wrong with the new approach to the a DOMCTL in this patch?
> >>
> >>The DOMCTL has been clearly identify as arm specific (there is "arm" in
> >>the name). Therefore it doesn't seem necessary to expose it for other
> >>architecture than ARM32 and ARM64.
> >
> >I didn't say there's anything actively wrong with it, all I said is that
> >I'm not particularly happy about it: Irrespective of its name it doesn't
> >look to be really arch-specific in the long run, plus it feels like the
> >data being set here should rather be specified right at domain
> >creation, or via a mechanism similar to x86'es HVM parameters (iirc
> >the value set here can't be changed once the domain got first
> >unpaused).
> 
> 
> TBH I choose this solution because I though you would be disagree with
> extending the domain create hypercall.
> 
> In long run, there will be more parameters such as the number of spis. All
> will be required at the same time. So the HVM parameters solution won't
> really help here.
> 
> However, I could give a look to extending the domain creation hypercall
> (xen_domctl_createdomain) to add arch specific field.
> 
> But I don't think it's Xen 4.5 material. So I would prefer to stay on this
> approach for this release because we'd like to have GICv3 guest support on
> Xen. Though I could rename the DOMCTL to DOMCTL_get_gic_version.

That is a bit unfortunate as it sounds like that for Xen 4.6 you will
then ditch this hypercall and focus on the new one? Won't this one then
be bitrotten?

> 
> Regards,
> 
> -- 
> Julien Grall

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