Re: REQUEST: Syncing tools/arch/arm64/include/asm/cputype.h with the kernel sources

On Mon, Mar 16, 2026 at 09:43:44AM +0000, Leo Yan wrote:

Hi Arnaldo,

[ + Mark ]

On Sun, Mar 15, 2026 at 10:43:03AM -0300, Arnaldo Carvalho de Melo wrote:

quoted

Hi,

	Can someone please address this perf build warning:

  make: Entering directory '/home/acme/git/perf-tools/tools/perf'
  BUILD:   Doing 'make -j32' parallel build
Warning: Kernel ABI header differences:
  diff -u tools/arch/arm64/include/asm/cputype.h arch/arm64/include/asm/cputype.h

I tried updating that header and got the problems below.

I just merged perf-tools with upstream, will push to tmp.perf-tools at:

https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools.git tmp.perf-tools

Thanks in advance,

Sorry that this issue has come up again.

A quick summary:

The plan was to extract the CPU ID definitions from cputype.h so that
kernel and userspace can share the same definitions.  This would avoid
keep syncing cputype.h between the kernel and userspace [1].

James worked on this a bit, and later Mark wanted to try a different
implementation.  However, we haven't posted formal patches yet.

To avoid extra burden on perf maintainers, I suggest removing the
cputype.h check in check-headers.sh.  In the short term, Arm developers
will take responsibility for keeping it up to date.  In the long term,
once the CPU ID refactoring is completed, we can do a proper cleanup of
cputype.h.

James, Mark, is this reasonable?

[1] https://lore.kernel.org/linux-perf-users/aFJ8bQh_30JMzF_-@J2N7QTR9R3/ (local)

Removing the check sounds good to me; that's one of the options I
suggested in [1]:

| The simple solution for now is to *NOT* update the userspace header,
| and to stop warning that this has diverged from the kernel header. 

I think it's fine if we need to manually update that header when
teaching the perf tool about specific CPUs.

Are you happy to spin a patch to remove the check?

Mark.