On 2021-04-07 22:18, Will Deacon wrote:

On Tue, Mar 30, 2021 at 06:39:47PM +0100, Marc Zyngier wrote:

quoted

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@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...

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