Re: KVM Processor cache size

Avi Kivity
2010-08-03T05:34:08Z

On 08/03/2010 01:22 AM, Anthony Liguori wrote:
> On 08/02/2010 08:08 AM, Avi Kivity wrote:
>>> I sent a patch to include the cache size when using -cpu host, but
>>> this has been n'acked because the benefit is not clear.
>>
>>
>> Anthony, why was this NACKed?
>
> I didn't NACK it.
>
> My concern is that we're still not handling live migration with -cpu
> host in any meaningful way. Exposing more details without addressing
> live migration is going to increase the likelihood of major failure.

-cpu host is never going to be live migratable unless your hosts are
exactly equal. Its goal is to get the best performance, not best
compatibility, similar to device assignment.

>
> We need to add cpuid information to live migration such that we can
> generate a graceful failure during migration.

Agreed, esp. as it contains state.

> Really, we shouldn't have taken -cpu host in the first place without
> this.

Disagreed. For live migration the user needs to specify cpuid precisely.

We do need to be able to specify the cache size parameters from the -cpu
description, but that shouldn't stop -cpu host.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.