Add option to skip cpu feature and model verification in libvirt and rely on qemu 'enforce' option

[Daniel P. Berrangé]

On Wed, Nov 23, 2022 at 05:58:41PM +0530, manish.mishra wrote:
> 
> On 23/11/22 5:44 pm, Daniel P. Berrangé wrote:
> > On Wed, Nov 23, 2022 at 12:51:39PM +0100, Jiri Denemark wrote:
> > > On Wed, Nov 23, 2022 at 11:41:03 +0000, Daniel P. Berrangé wrote:
> > > > Why can't it just use the exsting QEMU passthrough syntax we have.
> > > > I don't think we should be adding specifial support just for CPUs
> > > That would be nice, but the QEMU passthrough syntax cannot be used for
> > > changing options that libvirt already passes to QEMU. So using it would
> > > likely result in two separate -cpu options on QEMU command line. And it
> > > would not rule out the CPU verification code in libvirt. Remember, we
> > > add a default -cpu model in case there's none configured in the XML.
> > Two -cpu options isn't a problem, the latter will override the former,
> > which is fine from the level of support intended for QEMU passthrough
> > usage.
> > 
> > For the libvirt checking, isn't the 'check=none' attr sufficient
> > to skip checks libvirt does.
> > 
> > 
> > With regards,
> > Daniel
> 
> Actually even within check='none' libvirt does few checks e.g.
> virCPUValidateFeatures if feature string passed is proper and
> defined in libvirt. We could extend check='none' to remove even
> these kind of things. So Jiri suggested that making such kind
> of changes in general path is not good idea so discussion went
> to using separate cpu class <qemu:cpu>.

There is no need to remove any such check, as you wouldn't
be specifying any <cpu> element with custom features set,
so the virCPUValidateFeuatres check should not be creating
any problems at that point.

With regards,
Daniel
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