On 15/02/16 17:26, Will Deacon wrote:

On Thu, Feb 11, 2016 at 06:40:04PM +0000, Marc Zyngier wrote:

quoted

Having both VHE and non-VHE capable CPUs in the same system
is likely to be a recipe for disaster.

If the boot CPU has VHE, but a secondary is not, we won't be
able to downgrade and run the kernel at EL1. Add CPU hotplug
to the mix, and this produces a terrifying mess.

Let's solve the problem once and for all. If you mix VHE and
non-VHE CPUs in the same system, you deserve to loose, and this
patch makes sure you don't get a chance.

This is implemented by storing the kernel execution level in
a global variable. Secondaries will park themselves in a
WFI loop if they observe a mismatch. Also, the primary CPU
will detect that the secondary CPU has died on a mismatched
execution level. Panic will follow.

This should really be based on Suzuki's series for handling generic
mismatches:

http://lists.infradead.org/pipermail/linux-arm-kernel/2016-January/401727.html

To avoid growing a dependency on something that's unlikely to make it
for 4.6, I'd be inclined to drop your homegrown checks altogether amd
help Suzuki with his series as a separate activity (i.e. it needn't be
a blocker imo).

That's fine, I'll drop that one - we can revisit it and fold it into
Suzuki's series.

Thanks,

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