Re: [Xen-devel] [PATCH] xen: report PV capability in sysctl and use it in toolstack

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Nov 08, 2018 at 06:29:05PM +0000, Andrew Cooper wrote:
> On 08/11/18 18:08, Wei Liu wrote:
> > 0e2c886ef ("xen: decouple HVM and IOMMU capabilities") provided a
> > truth table for what `xl info` would report. In order to make the
> > table work xen will need to report its PV capability.
> >
> > Replace cap_directio with cap_pv in libxl IDL. It is safe to do so
> > because cap_directio has never been released. Revert to use
> > cap_hvm_directio to mark the availability of IOMMU, to save us from
> > providing a compatibility layer.
> >
> > Don't bump sysctl version number because we've already done so.
> >
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> 
> In principle, I think this is fine.  However, some observations.
> 
> Looking more closely at the matrix, we've got:
> 
>     pv      hvm     iommu           flags in xl info
>     0       0       x               n/a
>     0       1       0               hvm
>     0       1       1               hvm hvm_directio
>     1       0       0               NIL
>     1       0       1               directio
>     1       1       0               hvm
>     1       1       1               hvm hvm_directio directio
> 
> Wouldn't it make more sense to have pv and pv_directio, even if only as
> the end user visible string?

That would be fine by me. I didn't do it because I couldn't figure out
the difference between virt_caps and xen_caps.

> 
> > diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> > index 3b8f967651..41babb329e 100644
> > --- a/tools/libxl/libxl_types.idl
> > +++ b/tools/libxl/libxl_types.idl
> > @@ -1013,8 +1013,8 @@ libxl_physinfo = Struct("physinfo", [
> >      ("hw_cap", libxl_hwcap),
> >  
> >      ("cap_hvm", bool),
> > +    ("cap_pv", bool),
> >      ("cap_hvm_directio", bool),
> 
> Is it worth noting "# No longer HVM specific" here?

Sure.

Wei.

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