Re: [Qemu-devel] [PATCH] target-ppc: Add POWER8E_v2.1 CPU model.

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 07/08/2015 03:37 PM, David Gibson wrote:
> On Wed, Jul 08, 2015 at 02:10:28PM +1000, Alexey Kardashevskiy wrote:
>> On 07/08/2015 01:43 PM, David Gibson wrote:
>>> From: Andrea Bolognani <abologna@redhat.com>
>>>
>>> Add a missing PVR value for the POWER8E v2.1 CPU.  Information taken
>> >from the kernel cputable.
>>>
>>> Signed-off-by: Andrea Bolognani <abologna@redhat.com>
>>> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
>>> ---
>>>   target-ppc/cpu-models.c | 4 +++-
>>>   target-ppc/cpu-models.h | 1 +
>>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>>
>>> Alex,
>>>
>>> Not sure if this counts as a bugfix which can be merged now we're in
>>> the hard freeze.  The lack of it does mean we can't work on one of our
>>> dev machines which has this CPU.
>>
>>
>> Why is this a stopper? We stopped bothering with exact PVRs some time ago
>> and -cpu POWER8 or -cpu host still work.
>
> Andrea, can you clarify?
>
> I think it's because libvirt likes to specify a specific CPU - and if
> it gets the new PVR from the host, qemu won't understand it.


A specific CPU in this case is "POWER8", I added this specifically for 
libvirt (to allow migration between all versions of POWER8), it should not 
use versioned CPUs and it does not in powerkvm.

There is actually a patch to make this PVR masking/subclassing nicer, I 
replied to it with adding you in cc:, please have a look. Andreas Faerber 
had objections which I did not really grasp then.


-- 
Alexey