Re: [PATCH 10/10] KVM: PPC: Enable the PAPR CAP for Book3S

Alexander Graf
2011-08-10T07:59:41Z

Am 10.08.2011 um 06:42 schrieb Paul Mackerras <paulus@samba.org>:

> On Tue, Aug 09, 2011 at 06:31:48PM +0200, Alexander Graf wrote:
>
>> Now that Book3S PV mode can also run PAPR guests, we can add a PAPR cap and
>> enable it for all Book3S targets. Enabling that CAP switches KVM into PAPR
>> mode.
>
> Don't we want to enable it only for 64-bit hosts? Trying to run a
> PAPR guest on a 32-bit Book 3S host won't work very well, unless I am
> missing something...

I agree that it doesn't make sense, but if anything we should restrict it to 64-bit _guests_. you can also run 32-bit guests on 64-bit hosts.

And so far, we don't have a single interface setting PVR and PAPR mode at the same time, so you could still enable PAPR with a 64-bit guest CPU and then switch to a 32-bit CPU.

It'd be a nightmare to check all configurations on every setter function.

Unless...

We could introduce a sanity check function that gets executed every time we change PVR or enable PAPR. That could set a variable in the vcpu struct to indicate that the config is ok. We could then check that on vcpu_run.

Alex

>