Re: [PATCH] powerpc/pseries: Add POWER8NVL support to ibm,client-architecture-support call

[Thomas Huth <thuth@redhat.com>]

On 08.06.2016 03:14, Balbir Singh wrote:
> 
> On 31/05/16 20:32, Michael Ellerman wrote:
>> On Tue, 2016-05-31 at 12:19 +0200, Thomas Huth wrote:
>>> On 31.05.2016 12:04, Michael Ellerman wrote:
>>>> On Tue, 2016-05-31 at 07:51 +0200, Thomas Huth wrote:
>>>>> If we do not provide the PVR for POWER8NVL, a guest on this
>>>>> system currently ends up in PowerISA 2.06 compatibility mode on
>>>>> KVM, since QEMU does not provide a generic PowerISA 2.07 mode yet.
>>>>> So some new instructions from POWER8 (like "mtvsrd") get disabled
>>>>> for the guest, resulting in crashes when using code compiled
>>>>> explicitly for POWER8 (e.g. with the "-mcpu=power8" option of GCC).
>>>>>
>>>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>>>
>>>> So this should say:
>>>>
>>>>   Fixes: ddee09c099c3 ("powerpc: Add PVR for POWER8NVL processor")
>>>>
>>>> And therefore:
>>>>
>>>>   Cc: stable@vger.kernel.org # v4.0+
>>>>
>>>> Am I right?
>>>
>>> Right. (At least for virtualized systems ... for bare-metal systems,
>>> that original patch was enough). So shall I resubmit my patch with these
>>> two lines, or could you add them when you pick this patch up?
>>
>> Thanks, I'll add them here.
> 
> Don't we need to update IBM_ARCH_VEC_NRCORES_OFFSET as well?

D'oh! You're right, that needs to be changed, too! I'll send a fixup
patch once I've tested it...

By the way, there seems to be already a check for
ibm_architecture_vec[IBM_ARCH_VEC_NRCORES_OFFSET] != NR_CPUS in
prom_send_capabilities(), but it only prints out a warning which easily
gets lost in the kernel log ... I wonder whether we should rather stop
the boot there instead to catch this problem more easily?

 Thomas