Re: [PATCH 13/18] arm64: preserve x18 when CPU is suspended

Sami Tolvanen
2019-10-18T17:05:48Z

On Fri, Oct 18, 2019 at 9:49 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
> > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> > index fdabf40a83c8..9a8bd4bc8549 100644
> > --- a/arch/arm64/mm/proc.S
> > +++ b/arch/arm64/mm/proc.S
> > @@ -73,6 +73,9 @@ alternative_endif
> > stp x8, x9, [x0, #48]
> > stp x10, x11, [x0, #64]
> > stp x12, x13, [x0, #80]
> > +#ifdef CONFIG_SHADOW_CALL_STACK
> > + stp x18, xzr, [x0, #96]
>
> Could this be a str/ldr of just x18 rather than stp/ldp of x18 +
> garbage? Maybe there's no real cost difference, or some kind of
> alignment invariant?

Sure, this can be changed to str/ldr. I don't think there's a
noticeable difference in cost.

Sami