linux-kernel - Re: perf usage of arch/arm64/include/asm/cputype.h

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aFBYrQgx2m8Nd-iG@J2N7QTR9R3>
Date: Mon, 16 Jun 2025 18:47:25 +0100
From: Mark Rutland <mark.rutland@....com>
To: Leo Yan <leo.yan@....com>
Cc: Yicong Yang <yangyicong@...wei.com>,
	Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>,
	yangyicong@...ilicon.com, James Clark <james.clark@...aro.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	Ali Saidi <alisaidi@...zon.com>, Leo Yan <leo.yan@...aro.org>,
	Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	yangjinqian <yangjinqian1@...wei.com>,
	Douglas Anderson <dianders@...omium.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: perf usage of arch/arm64/include/asm/cputype.h

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:
> 
> [...]
> 
> > >> +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.