Re: [Qemu-devel] [PATCH] target/arm/kvm: gic: Prevent creating userspace GICv3 with KVM

[Christoffer Dall <christoffer.dall@linaro.org>]

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Hi Philippe,

On Mon, Feb 05, 2018 at 09:10:48PM -0300, Philippe Mathieu-Daudé wrote:
> 
> On 02/01/2018 05:53 PM, Christoffer Dall wrote:
> > KVM doesn't support emulating a GICv3 in userspace, only GICv2.  We
> > currently attempt this anyway, and as a result a KVM guest doesn't
> > receive interrupts and the user is left wondering why.  Report an error
> > to the user if this particular combination is requested.
> > 
> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> > ---
> >  target/arm/kvm_arm.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> > index ff53e9fafb..cfb7e5af72 100644
> > --- a/target/arm/kvm_arm.h
> > +++ b/target/arm/kvm_arm.h
> > @@ -234,6 +234,10 @@ static inline const char *gicv3_class_name(void)
> 
> Any reason why these functions are inlined in this include?

Not really sure what you mean?  What do you think would be a better
approach?

> 
> Also - not related to your patch - while gicv3_class_name() is
> self-explicit, gic_class_name() isn't (to me at least).

I think I tend to see 'gic' as GICv2 and 'gicv3' as GICv3 in QEMU, but I
don't remember the details of how you make the GIC be a proper GICv2 vs.
the 11mpcore version thingy.

> 
> There are many check for gic_version 1/2/3 in virt.c, which we could
> clean using more generic functions such gic_class_name(int gic_version)
> and Co.

Possibly.  Do note, that checking "which version of the GIC does this
board contain" is a separate thing from "which particular mechanism do I
use to emulate the GIC".

> 
> >          exit(1);
> >  #endif
> >      } else {
> > +        if (kvm_enabled()) {
> > +            error_report("Userspace GICv3 is not supported with KVM");
> > +            exit(1);
> 
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> 
> > +        }
> >          return "arm-gicv3";
> >      }
> >  }
> > 
> 
Thanks!
-Christoffer

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