Re: [Qemu-devel] [libvirt] Modern CPU models cannot be used with libvirt

[Itamar Heim <iheim@redhat.com>]

On 03/12/2012 10:19 PM, Ayal Baron wrote:
>
>
> ----- Original Message -----
>> On 03/12/2012 02:12 PM, Itamar Heim wrote:
>>> On 03/12/2012 09:01 PM, Anthony Liguori wrote:
>>>>
>>>> It's a trade off. From a RAS perspective, it's helpful to have
>>>> information about the host available in the guest.
>>>>
>>>> If you're already exposing a compatible family, exposing the
>>>> actual
>>>> processor seems to be worth the extra effort.
>>>
>>> only if the entire cluster is (and will be?) identical cpu.
>>
>> At least in my experience, this isn't unusual.
>
> I can definitely see places choosing homogeneous hardware and upgrading every few years.
> Giving them max capabilities for their cluster sounds logical to me.
> Esp. cloud providers.

they would get same performance as from the matching "cpu family".
only difference would be if the guest known the name of the host cpu.

>
>>
>>> or if you don't care about live migration i guess, which could be
>>> hte case for
>>> clouds, then again, not sure a cloud provider would want to expose
>>> the physical
>>> cpu to the tenant.
>>
>> Depends on the type of cloud you're building, I guess.
>>
>
> Wouldn't this affect a simple startup of a VM with a different CPU (if motherboard changed as well cause reactivation issues in windows and fun things like that)?

that's an interesting question, I have to assume this works though, 
since we didn't see issues with changing the cpu family for guests so far.