Re: [Xen-devel] [PATCH] clarify SHUTDOWN_suspend additional argument

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 8 May 2014, David Vrabel wrote:
> On 07/05/14 14:05, Stefano Stabellini wrote:
> > SCHEDOP_shutdown has a third argument that is unused on HVM and ARM
> > guests. Those guests pass 0 instead. Clarify the behaviour in the
> > hypercall description.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > diff --git a/xen/include/public/sched.h b/xen/include/public/sched.h
> > index a30b11d..c170556 100644
> > --- a/xen/include/public/sched.h
> > +++ b/xen/include/public/sched.h
> > @@ -77,8 +77,9 @@
> >   * @arg == pointer to sched_shutdown_t structure.
> >   *
> >   * If the sched_shutdown_t reason is SHUTDOWN_suspend then this
> > - * hypercall takes an additional extra argument which should be the
> > - * MFN of the guest's start_info_t.
> > + * hypercall takes an additional extra argument which should be:
> > + *  - the MFN of the guest's start_info_t for x86 PV guests;
> > + *  - 0 for x86 HVM guests and arm and arm64 guests.
> 
> Perhaps word this to reflect what the toolstack actually does?
> 
> * x86 PV guest must also set RDX (EDX for 32-bit guests) to the MFN
> * of the guest's start info page.  RDX/EDX is the third hypercall
> * argument.
 
That is better. It also the advantage on keeping the sched_op hypercall
always to 2 arguments on ARM, making the Linux side implementation
cleaner.
I'll respin both this patch and the corresponding Linux side.

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