Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/31/2017 10:33 AM, Ian Jackson wrote:
> Roger Pau Monné writes ("Re: [PATCH] xl: Add 'pvh' config option"):
>> On Fri, Mar 31, 2017 at 09:59:09AM -0400, Boris Ostrovsky wrote:
>>> That would make the toolstack have three guest types while the
>>> hypervisor has two.
> Is that a problem, conceptually ?  It seems to me to be accurate here.

To my eyes --- yes. Guest type is a basic concept and having toolstack
and the hypervisor disagree on how many guest types exist doesn't sound
right.

This doesn't mean that there shouldn't indeed be 3 types --- I agree
that from admin perspective PVH is nothing like HVM.

There is also another question, BTW: since PVH(v2) will first appear in
4.9 it would be nice to provide user-visible config options (i.e. 'pvh'
instead of or in addition to 'device_model_version=none') before
release, even if (proper) implementation is still under discussion.  But
perhaps the train has left the station already.

-boris

>
>> This was discussed on the PVHv1 removal patches. I sent a PVHv1 removal that
>> partially covered this (by adding a PVH guest type to libxl), but IMHO I find
>> it quite hard to add a guest type to libxl only (when it's not on the
>> hypervisor).
>>
>> It can certainly be done, but it's painful due to libxl having to filter the
>> output from Xen in order to properly detect guest types, since it cannot 
>> longer
>> use Xen values blindly.
> How many places in libxl have to change ?
>


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