[PATCH v2 3/3] arm64: kvm: add support for the extended 64bit ccsidr

[Sudeep Holla]

Hi Marc,

On 01/02/17 16:02, Marc Zyngier wrote:
[...]

> 
> I'm a bit worried about this patch. If we snapshot a VM on a 32bit
> CCSIDR system, and restore it on a 64bit CSSIDR system (or the reverse),
> what happens? My hunch is that we cannot restore the VM properly.
>

I agree. I had a look at QEMU as you suggested offline. Looks like QEMU
emulate these registers with predefined values for each core type. Also
it looks like it's not using the existing DEMUX_ID_CCSIDR

> Now, I'm questioning the need for having those altogether, as we do a
> lot of work to prevent the guest from actually using that geometry (and
> on a big-little system, this hardly works).
> 

If we can conclude there are no users for DEMUX_ID_CCSIDR, we can remove
it all together instead of introducing new one for 64bit.

Are there any other users of these interface provided by KVM after from
kvmtool and qemu ?

-- 
Regards,
Sudeep