Re: [GIT PULL] perf tools fixes for v7.0: 2nd batch

[Arnaldo Melo]

On March 24, 2026 1:17:18 PM GMT-03:00, Arnaldo Melo <arnaldo.melo@xxxxxxxxx> wrote:
>
>
>On March 24, 2026 1:12:08 PM GMT-03:00, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>>On Mon, 23 Mar 2026 at 03:57, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>>>
>>>       tools arch x86: Sync the msr-index.h copy with the kernel sources
>>>       tools headers UAPI: Sync linux/kvm.h with the kernel sources
>>>       tools headers UAPI: Sync x86's asm/kvm.h with the kernel sources
>>>       tools headers: Synchronize linux/build_bug.h with the kernel sources
>>
>>So I think we need to come up with some solution to *not* do this all,
>>because honestly, it's getting hugely annoying.
>>
>>And it's not annoying due to the unnecessary diffs per se, but because
>>this tool header sync then causes 'objtool' - which also uses some of
>>those headers - to be rebuilt, and then that causes *everything* to be
>>rebuilt.
>>
>>Just because the perf tree decided it needed to sync headers for
>>unexplained reasons.
>>
>>The docs say "this works surprisingly well". That *used* to be the
>>case. But with objtool also being affected, it really does *not* work
>>well at all.
>>
>>And no, the tools cannot use the kernel headers directly. That
>>*really* didn't work well, and required synchronizing kernel changes
>>with tooling changes, and was just a pain.
>>
>>So the "header copies" solved a real problem, but we need to figure
>>out something better.
>>
>>And honestly, the "something better" may be to just remove the
>>mindless check for "headers aren't 100% sync".
>>
>>Because 99% of the time nobody cares. This time, for example, the
>>header changes in question were comments and stuff that was inside a
>>__KERNEL__ guard.
>>
>>So how about just at least as a first step trying to remove the
>>warning that is actively detrimental, and only do header syncs when
>>there is a *real* reason for them?
>
>Yeah, I agree, annoying, I'll work on making this opt-in, i.e. no warnings by default, a new target to check if drift happened. 

Also maybe this is something for Sashiko or some other AI agent, to automate/suggest/do the sync when it makes sense and not just out of making it is in sync no matter what.

- Arnaldo

Sry, the previous reply didn't make it to lkml :-/