[libvirt] [PATCH 00/22] New CPU related APIs

[Collin Walling]

On 05/28/2018 03:44 PM, Chris Venteicher wrote:
> Quoting Jiri Denemark (2018-05-28 09:19:51)
>> On Wed, May 16, 2018 at 10:39:19 +0200, Jiri Denemark wrote:
>>> The current virConnectCompareCPU and virConnectBaselineCPU APIs are not
>>> very useful because they ignore what a hypervisor can do on the current
>>> host. This series adds two new APIs which are designed to work with
>>> capabilities of a specific hypervisor to provide usable results.
>>>
>>> The third CPU related API virConnectGetCPUModelNames is pretty useless
>>> too, but no new API with similar functionality is needed because domain
>>> capabilities XML already contains the relevant data.
>>
>> I made the suggested changes and pushed the series. Thanks for the
>> reviews.
>>
>> Jirka
> 
> Hi Jirka,
> 
> FYI I reviewed your patches too and everthing I found that was not already 
> identified was nitpick stuff but I do have a something I am wondering about...
> 
> The new hypervisor specific compare and baseline commands seem to depend on 
> qemuCaps being pre-populated with model data that is specific to a hypervisor 
> instance.
> 
> How do we make sure the qemuCaps are pre-populated with cpu model data for any 
> arbitrary hypervisor (with a different exec path, arch, etc) that we can issue 
> the hypervisor compare or baseline commands against?
> 
> Is it a case of executing a virsh command to populate qemuCaps for a non-default 
> hypervisor prior to issuing the hypervisor compare or baseline commands?
> 
> Sorry if a complete noob question or I missed the answer in previous mails.
> 
> Chris
> 

The qemuCaps are generated for each qemu binary upon startup of libvirt and are stored 
in /var/cache/libvirt/qemu/capabilities/

If you take a look at virQEMUCapsInitQMPMonitor in file qemu_capabilities, you'll see a 
bunch of functions with monitor calls that will probe qemu for its capabilities.

Since there can be a lot of different qemu caps that can exist on one system (due to different 
archs, different virttypes, etc), Jiri adds the ability to add parameters to specify which 
qemu capabilities file we want to pull data from.


>>
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-- 
Respectfully,
- Collin Walling