[PATCH v2 3/3] arm64: Allow nVHE impaired CPUs to boot without CONFIG_ARM64_VHE

[Marc Zyngier]

On 2021-04-07 22:18, Will Deacon wrote:
> On Tue, Mar 30, 2021 at 06:39:47PM +0100, Marc Zyngier wrote:
>> CPUs stuck in VHE mode need some additional care if the kernel
>> is compiled without CONFIG_ARM64_VHE.
>> 
>> Treat this case as another version of a mismatched boot, and
>> prevent KVM from being initialised. The machine will boot in
>> some bizarre state, using TPIDR_EL1 instead of TPIDR_EL2, but
>> otherwise be functional.
>> 
>> Signed-off-by: Marc Zyngier <maz at kernel.org>
>> ---
>>  arch/arm64/include/asm/virt.h | 18 +++++++++++++-----
>>  arch/arm64/kvm/va_layout.c    |  9 +++++++++
>>  2 files changed, 22 insertions(+), 5 deletions(-)
> 
> Hmm, I think we definitely need _something_ here, but it's a bit 
> annoying
> to put ourselves into this weird state just for the sake of one stupid
> machine.

Which is why I'm not keen at all on this patch, and I'm happy to see
the machine die a painful death. We really can't be blamed for 
terminally
buggy HW, which the M1 obviously is.

> What if we dropped CONFIG_ARM64_VHE and made the VHE code unconditional
> instead? Is there a good reason to allow it to be disabled nowadays?

What do we do for the other camp, aka people really wanting to run nVHE
without any command line parameter? I can't see why you'd want to do
that, but hey, that's only me.

I'd be quite happy to see CONFIG_ARM64_VHE go though. Let me know if you
want a patch doing that instead.

Thanks,

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