On Mon, Jun 16, 2025 at 05:08:11PM +0100, Leo Yan wrote:

On Mon, Jun 16, 2025 at 11:04:08PM +0800, Yicong Yang wrote:

[...]

quoted

quoted

quoted

+static bool is_perf_midr_in_range_list(u32 midr, struct midr_range
const *ranges)
+{
+       while (ranges->model) {
+               if (midr_is_cpu_model_range(midr, ranges->model,
+                                           ranges->rv_min, ranges->rv_max)) {
+                       return true;
+               }
+               ranges++;
+       }
+       return false;
+}

Maybe we can make it more general. For example, move this function into
a common header such as tools/perf/arch/arm64/include/cputype.h. Then,
util/arm-spe.c can include this header.

ok this sounds just like as before except rename the midr check function and modify the
users in perf. will do in below steps:
- move cpu_errata_set_target_impl()/is_midr_in_range_list() out of cputype.h
  since they're only used in the kernel with errata information
- introduce is_target_midr_in_range_list() in cputype.h to test certain MIDR
  is within the ranges. (is_perf_midr_in_range_list() only make sense in
  userspace and is a bit strange to me in a kernel header). maybe reimplement
  is_midr_in_range_list() with is_target_midr_in_range_list() otherwise there's
  no users in kernel
- copy cputype.h to userspace and make users use new is_target_midr_in_range_list()

this will avoid touching the kernel too much and userspace don't need to implement
a separate function.

My understanding is we don't need to touch anything in kernel side, we
simply add a wrapper in perf tool to call midr_is_cpu_model_range().

When introduce is_target_midr_in_range_list() in kernel's cputype.h,
if no consumers in kernel use it and only useful for perf tool, then
it is unlikely to be accepted.

I think all of this is just working around the problem that
asm/cputype.h was never intended to be used in userspace. Likewise with
the other headers that we copy into tools/.

If there are bits that we *want* to share with tools/, let's factor that
out. The actual MIDR values are a good candidate for that -- we can
follow the same approach as with sysreg-defs.h.

Other than that, I think that userspace should just maintain its own
infrastructure, and only pull in things from kernel sources when there's
a specific reason to. Otherwise we're just creating busywork.

Mark.