Re: [PATCH] KVM: PPC: e500: Don't hardcode PIR=0

Alexander Graf
2011-09-02T19:23:48Z

On 02.09.2011, at 20:14, Scott Wood wrote:

> On 09/02/2011 10:12 AM, Alexander Graf wrote:
>>
>> Am 02.09.2011 um 01:08 schrieb Scott Wood <scottwood@freescale.com>:
>>
>>> Signed-off-by: Scott Wood <scottwood@freescale.com>
>>
>> Patch description missing.
>
> It's not missing, it's just brief. :-)
>
> I suppose you could add "The hardcoded behavior prevents SMP support.
> QEMU shall specify the vcpu's PIR as the vcpu id".

Ok, let me get my head around this. Before, PIR was forced to 0 by the setup code and set_sregs with PIR != 0 failed. Now it's simply vcpu_id which is already the correct value. Why didn't I run into this failure? Why did SMP work for me at all then? Shouldn't the guest be completely confused and find two CPU 0s?

>
>> Also, since pir == vcpu_id now, can't we just remove pir?
>
> From sregs? Is that worth the compatibility breakage? We could define
> a new bit for ARCH206 without PIR, but older QEMU would then not see the
> other ARCH206 stuff.

Ugh. This is only in sregs. In KVM we already do use vcpu_id. Yes, all is fine there. I misread things as if we were having vcpu->pir :).

Alex