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Re: [Qemu-ppc] [PATCH v3] ppc: introduce CPUPPCState::cpu_dt_id


From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH v3] ppc: introduce CPUPPCState::cpu_dt_id
Date: Tue, 5 Nov 2013 07:00:39 +0100


Am 05.11.2013 um 02:48 schrieb Scott Wood <address@hidden>:

> On Tue, 2013-11-05 at 12:26 +1100, Alexey Kardashevskiy wrote:
>> On 11/05/2013 06:42 AM, Scott Wood wrote:
>>> On Mon, 2013-11-04 at 10:41 +0100, Alexander Graf wrote:
>>>> What we really have are 3 semantically separate entities:
>>>> 
>>>>  * QEMU internal cpu id
>>>>  * KVM internal cpu id
>>>>  * DT exposed cpu id
>>>> 
>>>> As you have noted, it's a good idea to keep the QEMU internal cpu id
>>>> linear, thus completely separate from the others. The DT exposed cpu id
>>>> should be 100% local to hw/ppc/spapr*.c. I don't think any code outside
>>>> of the DT generation and anything that accesses the "Virtual Processor
>>>> Number" in sPAPR needs to care about the DT cpu id. All that code is
>>>> 100% KVM agnostic.
>>> 
>>> This patch isn't just for sPAPR...  On e500 the DT cpu id is supposed to
>>> match the MPIC cpu id.
>> 
>> 
>> At least is my patch correct for e500?
> 
> I think so.
> 
>> I do not really know what is the difference between e500 and spapr in this 
>> part.
> 
> e500 does not have sPAPR, and if the DT ID is "100% local to
> hw/ppc/spapr*.c" then the MPIC code will have a problem.
> 
> Currently we don't support smt on e500 in QEMU, but e6500 (an
> e500-derivative) does have smt, so it could happen in the future.

Sure, at that point we add logic that syncs the kvm and dt ids to whatever the 
kernel expects from the e500 machine file.

The current logic that says "every Nth vcpu id is a core, the ones in between 
are threads" is fairly implementation specific to the spapr hv code, no?


Alex




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