Re: [libvirt] [PATCH 2/3] libxl: add support for CPUID features policy
On Thu, Jun 29, 2017 at 10:39:26 +0200, Marek Marczykowski-Górecki wrote:
On Thu, Jun 29, 2017 at 10:04:42AM +0200, Jiri Denemark wrote:
> On Thu, Jun 29, 2017 at 03:11:42 +0200, Marek Marczykowski-Górecki wrote:
> > Set CPU features in appropriate libxl structure.
> > Use old "xend" syntax, because it allow control over any bit and
libvirt
> > already have API for translating features to appropriate cpuid bits. And
> > also features naming in libxl do not match the one of libvirt in
> > multiple cases.
>
> How does the new syntax look like?
"host,tm=0,sse3=0"
Is "host" fixed there or are other CPU models supported too? If only
"host" is allowed, libxl driver should support host-passthrough mode
only and it would be pretty easy to map it to the libxl's syntax. The
following CPU XML
<cpu mode='host-passthrough'>
<feature name='avx' policy='disable'/>
<feature name='aes' policy='require'/>
</cpu>
could be directly translated into "host,avx=0,aes=1".
> And would it be actually better?
Maybe? But the new syntax use different names for many features (like
pni vs sse3, or sep vs sysenter), so it would require some ugly
translation table...
I don't a translation table would be ugly.
What I would really like here, is to get list of bits specified with
<feature ...>, _without_ those defined by <model>. And maybe even
without requiring <model> to be set at all.
That's what host-passthrough mode is for.
Jirka