Re: [PATCH 5/5] arm64: KVM: vgic-v2: Enable GICV access from HYP if access from guest is unsafe

Marc Zyngier
2016-08-19T14:54:25Z

On Fri, 19 Aug 2016 14:31:12 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:

> On 19 August 2016 at 14:05, Marc Zyngier <marc.zyngier@arm.com> wrote:
> > On 19/08/16 13:53, Peter Maydell wrote:
> >> Is it worth specifically saying "performance will be worse", or do we
> >> expect this to only happen on systems where the h/w can't permit direct
> >> access (as opposed to those with bad dt info) ?
> >
> > We cannot distinguish between the two, unfortunately. Even worse, ACPI
> > only gives us a base address, and not the size of the region. So even if
> > the HW was perfectly compliant with SBSA, we have to assume the worse case.
>
> Right, but if we expect this is mostly going to be "you just have
> to live with it on this hardware" there's less point in printing
> an alarming message, whereas if there's a significant subset of
> "dt is just wrong" cases then the alarm might help in getting them
> fixed, maybe...

That'd require some more infrastructure from the kernel's GIC driver
(which now provides the various base addresses), but I guess that we
can have a look as well.

Thanks,

M.
--
Jazz is not dead. It just smells funny.