Re: [Xen-devel] [PATCH] x86: Expose hypervisor's PVH support via xen_caps

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.05.14 at 17:20, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 23/05/14 16:08, Boris Ostrovsky wrote:
>> On 05/23/2014 11:00 AM, Andrew Cooper wrote:
>>> On 23/05/14 15:55, Boris Ostrovsky wrote:
>>>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
>>>> ---
>>>>   xen/arch/x86/setup.c | 5 +++++
>>>>   1 file changed, 5 insertions(+)
>>> If the plan is to try and PVH and HVM back into one mode as far as Xen
>>> is concerned, doesn't this become redundant?
>>
>> Yes, I was thinking about this but we currently don't have (or,
>> rather, I can't think of) a good way to determine whether we can start
>> a PVH guest. We can grep the log but that doesn't feel like a
>> particularly good solution.
>>
>> One option could be to postpone this patch until 4.5 freezes and see
>> whether we indeed followed up on the plan and if we didn't then
>> integrate it.

I don't see what 4.5 has to do with this - 4.4 already has PVH
support (it being experimental and DomU only imo doesn't matter
as far as feature reporting is concerned).

> My concern here is that if this patch gets accepted, it will have to say
> forever more as the cap strings are a very public API.

Depends how you view it - if this becomes indistinguishable from
PVH for the tools stack, it could also get dropped again. Otoh I
don't think it will (or even should) become indistinguishable, and
hence I'm not sure its functional folding with (most of) HVM would
actually be a valid reason to drop this indication again (or, if it
has to remain, to consider it deprecated and pointless).

Jan


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