Re: [Qemu-devel] State of KVM bits in linux-headers

[Jan Kiszka]

On 2012-01-11 20:32, Alexander Graf wrote:
> 
> On 11.01.2012, at 20:16, Jan Kiszka wrote:
> 
>> Hi,
>>
>> I'm a bit unhappy about the current state of our supposed to be
>> automatically sync'ed linux-headers directory in qemu. It has been
>> updated several times against undefined kernel trees, means against
>> neither a released version nor kvm.git. Now, if I run an update against
>> kvm.git + some local change, I get a churn of removals. Same will happen
>> when that local change ever goes upstream before the other stuff got
>> finally committed.
> 
> Yes, call me even more unhappy about it :(.
> 
>> Alex, it looks to me like this is mostly PPC stuff. Can you comment on
>> the origin and workflow? E.g. KVM_CAP_SW_TLB: This has been added half a
>> year ago but is not in any Linux release around. Fishy...
> 
> Ok, here's my workflow:
> 
>   * KVM: receive patches on the ML
>   * KVM: wait for reviews, review myself
>   * KVM: send out a pull request
>   -- this is the point in time where I assume the ABI can be considered 
> stable --
>   * QEMU: run update on the headers, because in a perfect world things should 
> hit kvm.git any day
>   * KVM: pull request gets reviews causing not-pulls or abi changes and lots 
> of churn because i need forever to pullreq again ;)

Likely, the last item has to be moved up by two steps...

> 
> I guess you see the problem. Hence I haven't pushed any kernel header updates 
> since I realized how badly broken that process was. However even the stuff 
> that's in qemu.git now hasn't managed to get upstream yet.

On the other hand, if I recall correctly, there were some complaint on
the list recently about a header update patch again a Linux -rc version.
Because it removed the limbo land stuff in the same run, of course.
That's very bad. I see the problem: ppc targets will no longer build, at
least with KVM enabled, right? But this needs to be resolved now.

> 
>> I would like to see us avoiding this in the future. Headers update
>> patches should mention the source and should not be merged until the ABI
>> changes actually made it at least into kvm.git. Same applies, of course,
>> to the functional changes related to that ABI. Otherwise we risk quite
>> some mess on everyone's side.
> 
> I agree.
> 
>> Another thing: KVM_CAP_PPC_HIOR has been removed again from the kernel
>> and also the header. Is there real free space now or will the cap
>> reappear? If there should better be a placeholder, let's add it (to the
>> kernel).
> 
> I will reappear with ONE_REG semantics.
> 

OK.

Then please clean up now so that update-linux-headers.sh can be used
again by "normal" developers. :)

Jan

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