Re: [PATCH 0/2] xen: Fix PV-only build

Jürgen Groß <[email protected]> Thu, 6 Aug 2026 14:00:22 +0200

Newsgroups	gmane.comp.emulators.xen.devel,gmane.linux.kernel
Message-ID	<[email protected]>

On 06.08.26 13:31, Jan Beulich wrote:
> On 06.08.2026 12:55, Juergen Gross wrote:
>> On 06.08.26 03:52, Jason Andryuk wrote:
>>> Allow disabling XEN_PVHVM for a PV-only.  A stub in the event channel
>>> code needs to be fixed first.
>>>
>>> Jason Andryuk (2):
>>>     xen/events: Fix xen_set_upcall_vector stub
>>>     xen/Kconfig: select XEN_PVHVM
>>>
>>>    arch/x86/xen/Kconfig             | 8 +++++---
>>>    drivers/xen/events/events_base.c | 2 +-
>>>    2 files changed, 6 insertions(+), 4 deletions(-)
>>>
>>
>> I did a comparison of a kernel built with your patches disabling XEN_PVHVM
>> and my patches with XEN_PVHVM_GUEST disabled.
>>
>> The kernel built with my patches is 6 bytes smaller than the one with your
>> patches.
> 
> Isn't this a sign of something else needing tweaking, somewhere?

This is a sign that there are probably only very few really HVM specific paths
(in the sense of: explicitly not marked as irrelevant for PV) in the kernel.
Yes, I'm sure you can find some more, but I'm really not sure this is relevant
for more than a handful of users.

>> So I don't see any reason to take your patches, which conflict with mine,
>> especially as my patches have a negative diffstat on source level, too.
> 
> Hmm, Jason's patches look to move things into a more adequate direction,
> though. In which case I think a negative diffstat becomes an irrelevant
> argument?

Depends on what you are looking for.

My take from this is that a PV-only kernel with Jason's patches is not really
adding any value, while my simplification is at least making things simpler
in terms of code volume and number of Xen related config options.

Of course it would be possible to have a smaller PV-only kernel, but as I said
already, there has been no public demand for that in the last years and the
downsides IMHO far outweigh the potential gain.

IMO the "adequate direction" regarding Xen specific kernel code is towards PVH
and not towards more PV specific tweaking. And I'm very sure the kernel
community outside of the Xen community is agreeing with me here.

Juergen

OpenPGP_0xB0DE9DD628BF132F.asc (application/pgp-keys, 3.6 KB)

-----BEGIN PGP PUBLIC KEY BLOCK-----
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=eeAB
-----END PGP PUBLIC KEY BLOCK-----

OpenPGP_signature.asc (application/pgp-signature, 495 B)

-----BEGIN PGP SIGNATURE-----

wsB5BAABCAAjFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAmp0d1YFAwAAAAAACgkQsN6d1ii/Ey/s
PQf/RmWSU8PmAFvgouFrYfNYILXmJGZhWhBd2gHdpMWHSOjgQFAmKhqIK42bjsNnyh1eF0crr+g7
m9O8qY+fd+fXcI6iwPa+RWDZHTGLxdYuI6TQX7OMsuaDRnTzHk+WacAwVfOSqvkDx0f2uagfxqef
sFhirnvS0wyiSKd9Qo3UGmFJGvKfiVdVYKfDb4y9TuOdxtM4E0BiFcyzYqWIWh+SHA3yoZXzwnAf
pyBpj/WERJZex8/+SEshJz1weNKMe7Z56P/12K2e4m83nndEF+qNOXRA89YAW5FCCb+Ri11VEJcm
AFCuNSIEYM1ZLI/qAx+nNLRZ8K75WKQrhe+gbd+/Ug==
=vN2B
-----END PGP SIGNATURE-----