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

From: Ian Campbell <ijc@hellion.org.uk>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH] ARM: HYP/non-sec: Add MIDR check to detect unsupported CPUs
Date: Wed, 06 Aug 2014 08:38:13 +0100	[thread overview]
Message-ID: <1407310693.23472.67.camel@dagon.hellion.org.uk> (raw)
In-Reply-To: <53DFA343.407@arm.com>

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? 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).

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.

Ian.