Re: [Xen-devel] [RFC PATCH KERNEL 0/4] x86/xen: untangle PV and PVHVM guest support code

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> writes:

> On 11/14/2016 01:21 PM, David Vrabel wrote:
>> On 14/11/16 17:17, Vitaly Kuznetsov wrote:
>>> Hi,
>>>
>>> I have a long-standing idea to separate PV and PVHVM code in kernel and 
>>> introduce Kconfig options to make it possible to enable the required
>>> parts only breaking the current 'all or nothing' approach.
>>>
>>> Motivation:
>>> - Xen related x86 code in kernel is rather big and it is unclear which
>>>   parts of it are required for PV, for HVM or for both. With PVH coming
>>>   into picture is becomes even more tangled. It makes it hard to
>>>   understand/audit the code.
>>>
>>> - In some case we may want to avoid bloating kernel by supporting Xen
>>>   guests we don't need. In particular, 90% of the code in arch/x86/xen/ is
>>>   required to support PV guests and one may require PVHVM support only.
>>>
>>> - PV guests are supposed to go away one day and such code separation would
>>>   help us to get ready.
>> All good reasons.

Good, let's do it then)

>>> This RFC adds XEN_PV Kconfig option and makes it possible to build PV-only
>>> and PVHVM-only kernels. It also makes it possible to disable Dom0 support.
>>> The series is incomplete and probably dirty in some places, I didn't pay
>>> much attention to the current PVH implementation as (as far as I
>>> understand) it is supposed to be replaced with PVHv2 but before investing
>>> more I'd like to get opinions whether such refactoring will be welcomed.
>> This series might be best done after PVHv1 is removed.  Boris, any
>> thoughts on the best approach here?
>
> I would prefer to wait until at least domU PVHv2 (together with removal
> of v1) happens. As soon as I am done with ACPI hotplug on the hypervisor
> side I will post the new version.

Sure, there is no rush here.

-- 
  Vitaly

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