Re: [Qemu-devel] virtio-gpu doesn't build if you do a linux-headers update from kvm/next

[Christian Borntraeger <borntraeger@de.ibm.com>]

Am 05.11.2015 um 13:32 schrieb Peter Maydell:
> On 5 November 2015 at 12:13, Gerd Hoffmann <kraxel@redhat.com> wrote:
>>> etc, because all the virtio_gpu definitions disappear from
>>> include/standard-headers/linux/virtio_gpu.h.
>>
>> Updates not yet in mainline, they are sitting in drm-next and should
>> land during the merge window (i.e. 4.4-rc1 should have them).
>>
>> I'd suggest to exclude virtio_gpu.h changes when updating linux headers
>> for the time being.
> 
> I would strongly prefer it if we could get to a point where
> we can say "kernel headers must only be updated from this tree"
> and be guaranteed that it always works. This used to be true
> with the tree in question being kvm/next, but it doesn't seem
> to be so now. If it's going to be common that we have header
> changes that don't go via kvm/next, maybe we need to coordinate
> a tree that merges together the abi-guaranteed-stable changes
> from different places before they hit mainline?

Yes I agree. In the end this might imply to only use Linus tree to
merge things in qemu. This is probably fine regarding the Linux tree,
as it has a  63/70 day cadence and we only synced from kvm/next after
rc4 or so. So this might defer for 4,5, or 6 weeks. 
One problem why people won't like that is that the QEMU releases are
not often enough, though, as missing the deadline will defer the feature
for 4 or 5 month.

2014-04-17 	Tag v2.0.0 
2014-08-01 	Tag v2.1.0 
2014-12-09 	Tag v2.2.0 
2015-04-24 	Tag v2.3.0 
2015-08-11 	Tag v2.4.0 
2015-12-10 	Tag v2.5.0

Maybe we should try to aim for a 3 month cadence for QEMU to reduce the 
pain of missing soft/hard freeze. -> maybe a topic for the next QEMU 
summit?


Christian