Re: [PATCH v20 03/14] KVM: arm64: Manage GCS access and registers for guests

[Lorenzo Stoakes (ARM)]

On Mon, Sep 07, 2026 at 03:55:43PM +0100, Mark Brown wrote:
> On Mon, Sep 07, 2026 at 03:14:34PM +0100, Lorenzo Stoakes (ARM) wrote:
> > On Fri, Sep 04, 2026 at 10:07:49PM +0100, Mark Brown wrote:
> > > On Fri, Sep 04, 2026 at 09:54:51AM +0100, Lorenzo Stoakes (ARM) wrote:
>
> > > I think the best thing overall would be to leave the runtime paths as
> > > they are and refuse to run with an architecturally invalid setup, that
> > > would avoid bloating the fast path.
>
> > Ack, it'd be nice to not have to worry about that.
>
> > Presumably we definitely want an oops on a GCS violation in general?
>
> Yes, the guest is going to want GCS exceptions delivering if they've
> enabled them and something triggers them.  It might also be relying on
> the GCS for stack traces even if nothing triggers any GCS related fault.

OK so the answer seems definitely to be disallowing the invalid config at
runtime then I think! :)

--
Cheers, Lorenzo