Re: [Xen-devel] [PATCH] arm/gic-v3: Fix driver probe fail on GICv4 hardware

[Julien Grall <julien.grall@xxxxxxx>]

Hello Shanker,

On 27/05/16 15:31, Shanker Donthineni wrote:
> > >    diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> > > index 1365b4a..56a47f5 100644
> > > --- a/xen/arch/arm/domain.c
> > > +++ b/xen/arch/arm/domain.c
> > > @@ -571,6 +571,11 @@ int arch_domain_create(struct domain *d, unsigned int 
> > > domcr_flags,
> > >                d->arch.vgic.version = GIC_V3;
> > >                break;
> > >
> > > +        case GIC_V4:
> > > +            config->gic_version = XEN_DOMCTL_CONFIG_GIC_V3;
> > > +            d->arch.vgic.version = GIC_V3;
> > > +            break;
> > As mentioned in my previous mail, there is no support of GICv4 in Xen. Although 
> > the GICv3 driver is supporting this hardware.So we should not advertise GIC_V4 
> > outside of the driver until Xen will get enough knowledge of GICv4 which will 
> > require sensible change in the generic code.
> GICv4 hardware is fully compatible to GICv3 and has an additional feature vLPI. 
>  We don't need any special driver or changes to current driver to support GICv4 
> for SPIs/LPIs in Xen just like Linux kernel.
>
> Confused, you are expecting gic_hw_version() should return GIC version number 
> '3' on on GICv4 hardware, right?
Because the function is misnamed. It returns the version of GIC 
supported by the driver to find the associated vGIC. Currently we only 
support GICv3 and GICv2. If other GIC version are supported, it is only 
because they are compatible.
This is a choice of the driver and should not be exposed/spread outside 
of the drivers until it is strictly necessary.
Anyway, Stefano may have a different opinion on this.

Regards,

--
Julien Grall

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