Re: expose host CPU features to guests

Daniel P. Berrange
2007-09-05T19:44:48Z

On Wed, Sep 05, 2007 at 10:34:45PM +0300, Avi Kivity wrote:
> Anthony Liguori wrote:
> > On Wed, 2007-09-05 at 20:45 +0300, danken-atKUWr5tajBWk0Htik3J/w@public.gmane.org wrote:
> >
> >> Hi,
> >>
> >> It's a pity not to use a host CPU feature if it is available. This patch
> >> exposes host CPU features to guests. It allows fine-tuning the presented
> >> features from the command-line.
> >>
> >> The code could use some serious clean ups, but I think it is interesting
> >> enough right now. I'd be happy to hear your opinion and suggestions.
> >> The diff are done against qemu cvs. I tried it with kvm, but I thinkg it
> >> should be useful also for kqemu.
> >>
> >
> > I like this idea but I have some suggestions about the general approach.
> > I think instead of defining another machine type, it would be better to
> > just have a command line option like -cpuid that took a comma separate
> > string of features with "all" meaning all features that the host has.
> >
> >
>
> I think qemu-cvs has a -cpu option for non-x86 which could be used for
> this. Agree machine types are the wrong approach.

Yep, machine types are already used to switch between a different concept
so using the new -cpu option would make sense. Could perhaps extend the
syntax so that instead of '-cpu TYPE' it used '-cpu TYPE,FEATURES' where
FEATURES was an optional list of CPU features to allow - though perhaps
with some shortcut for specifying 'match the host cpu type & features'.

Dan.
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