Re: [Qemu-devel] [PATCH] target-ppc: Add versions to server CPU descriptions

[Alexander Graf]

On 04.03.15 15:14, Andreas Färber wrote:
> Alex,
> 
> Am 04.03.2015 um 13:28 schrieb Alexander Graf:
>> On 04.03.15 02:31, Alexey Kardashevskiy wrote:
>>> 5b79b1c "target-ppc: Create versionless CPU class per family if KVM" added
>>> a dynamic CPU class registration with the name of the CPU family which
>>> QEMU is running on. For example, this allowed specifying "-cpu POWER7"
>>> on every version of POWER7 machine, not just the one which POWER7 was
>>> an alias of. I.e. before 5b79b1c, "-cpu POWER7" would not work on real
>>> POWER7 2.1 and would work on POWER7 2.3 only. The same story for POWER8.
>>>
>>> However that patch broke POWER5+ support as POWER5+ CPU uses the same
>>> name as the CPU class so dynamic registering of the POWER5+ class failed.
>>>
>>> This redefines POWER5+ server CPUs by adding a version to them and adding
>>> an alias for TCG case. KVM will use dynamically registered CPUs.
>>>
>>> While we are here, do the same for 970 CPU.
>>>
>>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>>
>> Thanks, applied to ppc-next.
> 
> As Alexey predicted, I object.
> 
> The 970 part looks good and could be applied immediately if it were a
> separate patch.
> 
> But the POWER5+ part I have my doubts about: Was there really a v0.0???

IIUC most IBM POWER PVRs are regular in that their lower 16 bits are
major/minor. The PVR we have as "POWER5+" has those bits as 0, thus v0.0
is the correct translation of that.

Whether that CPU ever existed is a different question and arguably out
of scope for the patch.

> Others start with v1.0 and I have:
> 
> revision      : 2.1 (pvr 003b 0201)

I wouldn't object to removing the v0.0 version altogether and just make
POWER5+ be an alias to v2.1 instead. But that's something for a
follow-up patch ;).


Alex