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

Am 10.08.2011 um 06:42 schrieb Paul Mackerras [off-list ref]:

On Tue, Aug 09, 2011 at 06:31:48PM +0200, Alexander Graf wrote:
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quoted

Now that Book3S PV mode can also run PAPR guests, we can add a PAPR cap a=

nd

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enable it for all Book3S targets. Enabling that CAP switches KVM into PAP=

R

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mode.

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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 th=
e 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 c=
hange PVR or enable PAPR. That could set a variable in the vcpu struct to in=
dicate that the config is ok. We could then check that on vcpu_run.


Alex

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