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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 5 Nov 2014, Ian Campbell wrote:
> On Wed, 2014-11-05 at 10:31 +0000, Stefano Stabellini wrote:
> > On Wed, 5 Nov 2014, Ian Campbell wrote:
> > > > +         * hardware GIC. Only the value XEN_DOMCTL_CONFIG_GIC_DEFAULT
> > > > +         * is allowed. The DOMCTL will return the actual version of the
> > > > +         * GIC.
> > > > +         */
> > > > +        if ( domctl->u.configuredomain.gic_version != 
> > > > XEN_DOMCTL_CONFIG_GIC_DEFAULT )
> > > > +            return -EOPNOTSUPP;
> > > 
> > > EOPNOTSUPP doesn't seem quite right. EPARM  or EINVAL perhaps?
> > > 
> > > I'm also tempted to suggest that we should accept gic_version == the hw
> > > value, i.e. by moping the switch below up and including
> > >         && domctl->u.configuredomain.gic_version != gic_version
> > > in the condition.
> > 
> > I suggested to use -EOPNOTSUPP because one day we want to be able to use
> > this hypercall to choose a specific gic_version for the guest domain,
> > including gicv2 on gicv3 hardware for example.
> 
> Why is EOPNOTSUPP an appropriate error code for that though?

Because at the moment we don't support this use case? If we did we would
be OK with the user passing gic_version = 2 for example.

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