[libvirt] [PATCH v3 2/5] libxl: add support for PVH

[Jim Fehlig]

On 10/3/18 5:59 PM, Jim Fehlig wrote:
> On 10/3/18 3:25 PM, Marek Marczykowski-Górecki wrote:
>> On Wed, Oct 03, 2018 at 03:13:30PM -0600, Jim Fehlig wrote:
>>> On 10/2/18 4:50 PM, Jim Fehlig wrote:
>>>> On 9/30/18 8:15 PM, Marek Marczykowski-Górecki wrote:
>>>>> Since this is something between PV and HVM, it makes sense to put the
>>>>> setting in place where domain type is specified.
>>>>> To enable it, use <os><type machine="xenpvh">...</type></os>. It is
>>>>> also included in capabilities.xml, for every supported HVM guest type - it
>>>>> doesn't seems to be any other requirement (besides new enough Xen).
>>>>>
>>>>> Signed-off-by: Marek Marczykowski-Górecki <marmarek at invisiblethingslab.com>
>>>>> ---
>>>>> Changes in v2 proposed by Jim:
>>>>>    - use new_arch_added var instead of i == nr_guest_archs for clarity
>>>>>    - improve comment
>>>>>    - adjust for now required Xen >= 4.6 (remove part for Xen < 4.5)
>>>>>
>>>>> Changes in v3:
>>>>>    - limit VIR_DOMAIN_OSTYPE_XEN -> VIR_DOMAIN_OSTYPE_LINUX conversion to
>>>>>    Xen PV only
>>>>>    - do not accept VIR_DOMAIN_OSTYPE_LINUX for PVH
>>>>>    - fix reported capabilities for PVH - remove hostdev passthrough and
>>>>>    video/graphics
>>>>
>>>> No video, graphics or hostdev passthrough - bummer. Begs the question:
>>>> what to do with PVH XML config containing these devices? Reject it?
>>>> Silently ignore? I'll also need to remember to enable these as PVH gains
>>>> support for the devices.
>>>>
>>>>>    - use #ifdef LIBXL_DOMAIN_TYPE_PVH instead of hypervisor version to
>>>>>    check for PVH support
>>>>
>>>> This is a much better approach than the version check. I should have
>>>> thought of that earlier, sorry.
>>>
>>> Actually it is not. LIBXL_DOMAIN_TYPE_PVH is a value in the enum
>>> libxl_domain_type. Too bad PVH support isn't advertised in libxl.h with
>>> something like LIBXL_HAVE_PVH. Looks like we are stuck with the version
>>> check :-(.
>>
>> Hmm, but that version check is a runtime check. How to fix compile error
>> regarding missing LIBXL_DOMAIN_TYPE_PVH then? Let configure check that
>> and define some HAVE_xxx?
> 
> AFAICT, PVH support actually came in Xen 4.10
> 
> commit 27f826844d3666f151e86d66198583757cccbbed
> Author: Roger Pau Monne <roger.pau at citrix.com>
> Date:   Fri Sep 22 16:25:07 2017 +0100
> 
>      libxl: introduce a PVH guest type
> 
> git describe --contains 27f826844d3
> 4.10.0-rc1~219
> 
> And the only thing in that commit to check is the addition of 
> LIBXL_DOMAIN_TYPE_PVH to the libxl_domain_type enum. I think we'll have to check 
> it with AC_COMPILE_IFELSE. I've been fiddling with the below patch, which at 
> least works on a Xen >= 4.10. Can you check it on Xen < 4.10 too, and squash it 
> into your series?

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