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

Scott Wood
2011-09-02T19:35:25Z

On 09/02/2011 02:23 PM, Alexander Graf wrote:
>
> 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?

I was wondering about that myself. It looks like PIR isn't used much in
Linux on e500v2. There's no msgsnd. It's used to for
__secondary_hold_acknowledge, but that has a silent timeout.

-Scott