Re: [Xen-devel] [PATCH v6a 17/17] xen/arm: Restrict saving of gic register for idle domain

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-07-01 at 11:54 +0530, Vijay Kilari wrote:
> Hi Julien,
> 
> On Fri, Jun 27, 2014 at 8:28 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> > On 27/06/14 15:45, Ian Campbell wrote:
> >>
> >> On Thu, 2014-06-26 at 15:33 +0100, Julien Grall wrote:
> >>>
> >>> Hi Vijay,
> >>>
> >>> On 06/26/2014 06:34 AM, vijay.kilari@xxxxxxxxx wrote:
> >>>>
> >>>> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> >>>>
> >>>> Check for idle domain is missing before saving gic context
> >>>
> >>>
> >>> Can you be a bit more verbose to explain why we don't need to save
> >>> context for idle vcpu?
> >>
> >>
> >> There's lots of state you don't need to save for an idle domain, this
> >> one seems pretty clear cut to me.
> >
> >
> > Right. Actually, for a lambda developer it's not clear why we add non-stop
> > is_idle_vcpu on every save/restore functions.
> > As the Xen will always stay to hyp mode when the idle VCPU is running, why
> > do we simply skip ctx_to/ctx_from?
> >
> > It would make more sense and we will be able to put a big comment to clearly
> > explain how idle VCPU works.
> 
>    My knowledge on this topic is limited to explain in detail how idle
> VCPU worksin Xen.

I don't expect you to. What is needed is a more thorough check/cleanup
of the save/restore paths WRT the idle cpus and what needs to (not) be
saved. I don't expect you to do that either though.

Ian.


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