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

[Marc Zyngier <marc.zyngier@arm.com>]

On 06/08/14 10:49, Mark Rutland wrote:
> 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.

I know at least of one for which this is the case... which makes
switching the interrupts from Group0 to Group1 a fun adventure.

	M.
-- 
Jazz is not dead. It just smells funny...