[PATCH 5/6] arm64: Add the arm64.nosme command line option

[Marc Zyngier]

On Mon, 27 Jun 2022 18:04:05 +0100,
Mark Brown <broonie at kernel.org> wrote:
> 
> [1  <text/plain; us-ascii (7bit)>]
> On Mon, Jun 27, 2022 at 04:14:11PM +0100, Marc Zyngier wrote:
> 
> > +.Linit_sme:	/* SME register access and priority mapping */
> > +	msr	cptr_el2, x0			// Disable SME traps
> > +	bic	x0, x0, #CPTR_EL2_TSM
> > +	msr	cptr_el2, x0
> 
> Should the first msr there be a mrs?  If not it should probably have a
> comment explaining what it's doing.

Duh. Copy-paste programming, I'm sure it'll go far. :-/

> 
> > +	mov	x1, #0				// SMCR controls
> > +
> > +	mrs_s	x2, SYS_ID_AA64SMFR0_EL1
> > +	ubfx	x2, x2, #ID_AA64SMFR0_FA64_SHIFT, #1 // Full FP in SM?
> > +	cbz	x2, .Lskip_sme_fa64
> 
> I'm sure any firmware authors who enable SME will remember to also
> enable FA64 if it's supported in their hardware!

I could add check the override here too. It is a bit ugly as SMFR0
isn't encoded as 4 bit features, but hey, why not.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.