On 04.07.2017 15:02, Greg Kurz wrote:
> On Tue, 4 Jul 2017 21:41:51 +1000
> David Gibson <da...@gibson.dropbear.id.au> wrote:
>
>> On Tue, Jul 04, 2017 at 01:15:00PM +0200, Greg Kurz wrote:
>>> On Tue, 4 Jul 2017 13:01:26 +0200
>>> Laurent Vivier <lviv...@redhat.com> wrote:
>>>
>>>> Commit 5f3066d ("target/ppc: Allow workarounds for POWER9 DD1")
>>>> disables compatibility mode for POWER9 DD1 to allow to
>>>> boot on POWER9 DD1 host with KVM.
>>>>
>>>> As the workaround has been added in kvmppc_host_cpu_class_init(),
>>>> it applies only on CPU created with "-cpu host".
>>>> As we want to be able to use also "-cpu POWER9" on a POWER9 DD1
>>>> host, this patch moves the workaround from kvmppc_host_cpu_class_init()
>>>> to init_proc_POWER9().
>>>>
>>>
>>> As with ppc_cpu_initfn() in your previous version, init_proc_POWER9() is
>>> called for every CPU instance.. ie, all CPU will adjust the @pcr_supported
>>> class attribute...
>>
>> Ah.. yeah.. I didn't notice that before. That's definitely not right.It's a hack for DD1 which will likely be removed soon again anyway (as soon as the DD1 hardware is not in use anymore), so I think it's ok for such a temporary solution? >>> What about moving the workaround to ppc_POWER9_cpu_family_class_init() >>> instead ? This would just require to expose mfpvr() in some header. >> >> Yeah, as someone else pointed out using the host PVR is also >> definitely not right (unless you're in a function specifically >> connected to the host cpu class). >> > > I agree but the root issue is that we accept to pass -cpu POWER9 instead of > -cpu host with -enable-kvm. And the host cpu class isn't involved in this > case. Allowing -cpu POWERx with -enable-kvm was likely a bad idea, but we've agree with libvirt that we support this, so we can't revert this feature so easily without changing libvirt first. Thomas
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