[U-Boot] [PATCH] ARM: HYP/non-sec: Add MIDR check to detect unsupported CPUs

[Mark Rutland <mark.rutland@arm.com>]

On Wed, Aug 06, 2014 at 08:38:13AM +0100, Ian Campbell wrote:
> On Mon, 2014-08-04 at 16:14 +0100, Marc Zyngier wrote:
> 
> > My personal feeling is that booting in secure mode is always the wrong
> > thing to do.
> 
> FWIW I agree.
> 
> > If you want to go down the road of a single bootloader that is able to
> > run on several SOCs, then do it the proper way: parse the device tree
> > and have separate constraints for your SoC. But please don't blacklist
> > random cores just because it fits your environment.
> 
> I think there is a CPU feature register which indicates whether support
> for HYP mode is present, isn't there?

ID_PFR1[15:12] should tell you if the CPU has the virtualization
extensions.

> In which case a tolerable fix for now (going all the way DT is a big
> yakk to shave...) would be to use that to decide between booting in
> NS.HYP vs NS.SVC (nb: not NS.HYP vs S.SVC).

That sounds ideal.

> I don't recall if the GIC has a feature bit for the security extensions,
> but if not then inferring it from the CPUs support wouldn't be the worst
> thing in the world under the circumstances.

GICD_TYPER[10] (SecurityExtn) should tell you if the GIC has the
security extensions. I don't know whether you'll encounter a platform
where the CPU and GIC are mismatched w.r.t. security extensions.

Mark.