[PATCH 24/35] arm64: mte: Switch GCR_EL1 in kernel entry and exit

[Andrey Konovalov]

On Thu, Aug 27, 2020 at 12:38 PM Catalin Marinas
<catalin.marinas at arm.com> wrote:
>
> On Fri, Aug 14, 2020 at 07:27:06PM +0200, Andrey Konovalov wrote:
> > @@ -957,6 +984,7 @@ SYM_FUNC_START(cpu_switch_to)
> >       mov     sp, x9
> >       msr     sp_el0, x1
> >       ptrauth_keys_install_kernel x1, x8, x9, x10
> > +     mte_restore_gcr 1, x1, x8, x9
> >       scs_save x0, x8
> >       scs_load x1, x8
> >       ret
>
> Since we set GCR_EL1 on exception entry and return, why is this needed?
> We don't have a per-kernel thread GCR_EL1, it's global to all threads,
> so I think cpu_switch_to() should not be touched.

Dropping this line from the diff leads to many false-positives... I'll
leave this to Vincenzo.