Re: [Qemu-devel] [PATCH] Add definitions for current cpu models..

[john cooper <john.cooper@redhat.com>]

Jamie Lokier wrote:
> john cooper wrote:
>> As before a cpu feature 'check' option is added which warns when
>> feature flags (either implicit in a cpu model or explicit on the
>> command line) would have otherwise been quietly unavailable to a
>> guest:
>>
>>     # qemu-system-x86_64 ... -cpu Nehalem,check
>>     warning: host cpuid 0000_0001 lacks requested flag 'sse4.2' [0x00100000]
>>     warning: host cpuid 0000_0001 lacks requested flag 'popcnt' [0x00800000]
> 
> That's a nice feature.  Can we have a 'checkfail' option which refuses
> to run if a requested capability isn't available?  Thanks.

Certainly, others have requested the same.  Let's resolve
the issue at hand first.

> I foresee wanting to iterate over the models and pick the latest one
> which a host supports - on the grounds that you have done the hard
> work of ensuring it is a reasonably good performer, while "probably"
> working on another host of similar capability when a new host is made
> available.

That's a fairly close use case to that of safe migration
which was one of the primary motivations to identify
the models being discussed.  Although presentation and
administration of such was considered the domain of management
tools.

-john

-- 
john.cooper@redhat.com