[libvirt] [PATCH v2 0/8] libxl: PVHv2 support

[Jim Fehlig]

On 9/18/18 6:50 PM, Marek Marczykowski-Górecki wrote:
> This is a respin of my old PVHv1 patch[1], converted to PVHv2.
> Should the code use "PVH" name (as libxl does internally), or "PVHv2" as in
> many places in Xen documentation? I've chosen the former, but want to confirm
> it.

 From libvirt's perspective it should be "PVH". If anything, the Xen 
documentation should change. AFAIK the various PVH attempts/names (PVHv1, 
hvmlite, PVHv2, ...) have merged to simply be known as "PVH".

> 
> Also, not sure about VIR_DOMAIN_OSTYPE_XENPVH (as discussed on PVHv1 patch) -
> while it will be messy in many cases, there is
> libxl_domain_build_info.u.{hvm,pv,pvh} which would be good to not mess up.
> Also, PVHv2 needs different kernel features than PV (CONFIG_XEN_PVH vs
> CONFIG_XEN_PV), so keeping the same VIR_DOMAIN_OSTYPE_XEN could be
> confusing.
> On the other hand, libxl_domain_build_info.u.pv is used in very few places (one
> section of libxlMakeDomBuildInfo), so guarding u.hvm access with
> VIR_DOMAIN_OSTYPE_HVM may be enough.
> For now I've reused VIR_DOMAIN_OSTYPE_XEN - in the driver itself, most of
> the code is the same as for PV.

I should have read your v1 cover letter closer and agreed on the approach before 
spending time looking at code :-). But in the end I still think the OS type is 
VIR_DOMAIN_OSTYPE_XEN with the machine attribute specifying PV vs PVH. I use the 
fact that both OS types are modified to run on Xen to rationalize using 
VIR_DOMAIN_OSTYPE_XEN for both. Perhaps it would be best for a third opinion and 
Daniel (cc'd) can chime in.

> Since PVHv2 relies on features in newer Xen versions, I needed to convert also
> some older code. For example b_info->u.hvm.nested_hvm was deprecated in favor
> of b_info->nested_hvm. While the code do handle both old and new versions
> (obviously refusing PVHv2 if Xen is too old), this isn't the case for tests.
> How it should be handled, if at all?

Due to the compilation error in patch 5, I haven't checked patches 6-8 on xen < 
4.9, which may help me understand the problem you describe. Sorry it is not 
obvious to me from the reading.

Regards,
Jim