On Mon, Apr 22, 2013 at 02:37:06PM -0600, Eric Blake wrote:
> On 04/22/2013 01:00 PM, Eduardo Habkost wrote:
> > This property will be useful for libvirt, as libvirt already has logic
> > based on low-level feature bits (not feature names), so it will be
> > really easy to convert the current libvirt logic to something using the
> > "feature-words" property.
> >
> > The property will have two main use cases:
> > - Checking host capabilities, by checking the features of the "host"
> > CPU model
> > - Checking which features are enabled on each CPU model
> >
> > Example output:
> >
> > $ ./QMP/qmp --path=/tmp/m qom-get --path=/machine/unattached/device[1] --property=feature-words
>
> If I'm not mistaken, the QMP counterpart that libvirt will use is:
>
> { "execute":"qom-get",
> "arguments": { "path":"/machine/unattached/device[1]",
> "property":"feature-words" } }
Yes, but note that libvirt needs to look for the X86CPU objects, to find
the actual path as there's no guarantee that it will always be
/machine/unattached/devices[1]. Maybe the CPU hotplug work will end up
offering a predictable path for the X86CPU objects, but this is not
available yet.
>
> > item[0].cpuid-register: EDX
> > item[0].cpuid-input-eax: 2147483658
> > item[0].features: 0
> > item[1].cpuid-register: EAX
> > item[1].cpuid-input-eax: 1073741825
> > item[1].features: 0
> > item[2].cpuid-register: EDX
> > item[2].cpuid-input-eax: 3221225473
> > item[2].features: 0
> > item[3].cpuid-register: ECX
> > item[3].cpuid-input-eax: 2147483649
> > item[3].features: 101
> > item[4].cpuid-register: EDX
> > item[4].cpuid-input-eax: 2147483649
> > item[4].features: 563346425
> > item[5].cpuid-register: EBX
> > item[5].cpuid-input-eax: 7
> > item[5].features: 0
> > item[5].cpuid-input-ecx: 0
> > item[6].cpuid-register: ECX
> > item[6].cpuid-input-eax: 1
> > item[6].features: 2155880449
> > item[7].cpuid-register: EDX
> > item[7].cpuid-input-eax: 1
> > item[7].features: 126614521
>
> And this would then be returned as a JSON array containing struct
> members looking like this:
>
> > +{ 'type': 'X86CPUFeatureWordInfo',
> > + 'data': { 'cpuid-input-eax': 'int',
> > + '*cpuid-input-ecx': 'int',
> > + 'cpuid-register': 'X86CPURegister32',
> > + 'features': 'int' } }
Yes.
>
> Looks reasonable (and better than what we've had in the past!), although
> I'll let Jiri Denemark give final say on whether it meets libvirt's needs.
Thanks for the feedback!
--
Eduardo
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