[OS-BUILD PATCH] [redhat] perf: enable CoreSight support

[Michael Petlan (via Email Bridge)]

From: Michael Petlan

[redhat] perf: enable CoreSight support

Bugzilla: https://bugzilla.redhat.com/1877192

Decoding CoreSight needs opencsd-devel package at build-time and
opencsd package as runtime dependency. This feature is aarch64-only.

Signed-off-by: Michael Petlan

diff --git a/redhat/kernel.spec.template b/redhat/kernel.spec.template
index blahblah..blahblah 100755
--- a/redhat/kernel.spec.template
+++ b/redhat/kernel.spec.template
@@ -550,6 +550,9 @@ BuildRequires: libtraceevent-devel
 %ifnarch %{arm} s390x
 BuildRequires: numactl-devel
 %endif
+%ifarch aarch64
+BuildRequires: opencsd-devel >= 1.0.0-2
+%endif
 %endif
 %if %{with_tools}
 BuildRequires: gettext ncurses-devel
@@ -2073,8 +2076,11 @@ InitBuildVars
 %endif
 %endif

+%ifarch aarch64
+%global perf_build_extra_opts CORESIGHT=1
+%endif
 %global perf_make \
-  %{__make} %{?make_opts} EXTRA_CFLAGS="${RPM_OPT_FLAGS}" LDFLAGS="%{__global_ldflags}" %{?cross_opts} -C tools/perf V=1 NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 WERROR=0 NO_LIBUNWIND=1 HAVE_CPLUS_DEMANGLE=1 NO_GTK2=1 NO_STRLCPY=1 NO_BIONIC=1 LIBBPF_DYNAMIC=1 LIBTRACEEVENT_DYNAMIC=1 prefix=%{_prefix} PYTHON=%{__python3}
+  %{__make} %{?make_opts} EXTRA_CFLAGS="${RPM_OPT_FLAGS}" LDFLAGS="%{__global_ldflags}" %{?cross_opts} -C tools/perf V=1 NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 WERROR=0 NO_LIBUNWIND=1 HAVE_CPLUS_DEMANGLE=1 NO_GTK2=1 NO_STRLCPY=1 NO_BIONIC=1 LIBBPF_DYNAMIC=1 LIBTRACEEVENT_DYNAMIC=1 %{?perf_build_extra_opts} prefix=%{_prefix} PYTHON=%{__python3}
 %if %{with_perf}
 # perf
 # make sure check-headers.sh is executable

--
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1167

[Mark Salter (via Email Bridge)]

From: Mark Salter on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1167#note_5958162...

Acked-by: Mark Salter 
(via approve button)

[Justin Forbes (via Email Bridge)]

From: Justin Forbes on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1167#note_5958255...

Curious on this, as Fedora has been building with CORESIGHT for a bit now
(since July 2020). We did not case the changes on arch, and simply added
openscd-devel as a buildreq for everyone and pass CORESIGHT=1 to perf_make.
This builds fine across all arches, even though it is unnecessary.   As
coresight is an arm specific thing, it is really only used in arch/arm/util/
files and shouldn't be a problem for other architectures.  Which makes me ask,
do we trade spec complexity for more specific build command line, or do we go
the simple spec route and expect it to continue working?

[Michael Petlan (via Email Bridge)]

From: Michael Petlan on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1167#note_5965007...
> Justin Forbes commented:
>
> Curious on this, as Fedora has been building with CORESIGHT for a bit now

(since July 2020). We did not case the changes on arch, and simply added
openscd-devel as a buildreq for everyone and pass CORESIGHT=1
> to perf_make. This builds fine across all arches, even though it is

unnecessary. As coresight is an arm specific thing, it is really only used in
arch/arm/util/ files and shouldn't be a problem for other
> architectures. Which makes me ask, do we trade spec complexity for more

specific build command line, or do we go the simple spec route and expect it
to continue working?

I prefer cutting this down to be arm-specific and "trade the spec file
complexity",
since I see no reason for x86 (and other arch) customers (which I believe is a
majority)
to install completely useless packages.

I tend to the idea that we should keep RHEL composes tiny, since it looks
that this is the strategy for it as a platform. And sacrificing few more
lines in spec to this is not that high price. Also, there already are arch-
specific build-reqs.

A better question is, whether linking opencsd would allow the x86 users to
e.g. analyse the coresight trace from perf.data obtained on aarch64. In
such case, it would make sense. But, to be honest, I don't see this ability
there, I haven't noticed any customer interest in that, any mention in the
docs about it (maybe I am missing something!), so I decided this way.

But as I say, extended functionality is an argument for linking it everywhere,
spec simplicity seems not to be enough in my opinion.

[Justin Forbes (via Email Bridge)]

From: Justin Forbes on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1167#note_5967804...
> I prefer cutting this down to be arm-specific and "trade the spec file

complexity", since I see no reason for x86 (and other arch) customers (which I
believe is a majority) to install completely useless packages.

This is valid. I wasn't thinking about the dep on install, only the build
side. As I didn't make the original change in Fedora, I was just verifying
that we had this functionality and saw how it was put in.
> A better question is, whether linking opencsd would allow the x86 users to

e.g. analyse the coresight trace from perf.data obtained on aarch64. In such
case, it would make sense.

I would have to look at the code to see, or Fedora has been built this way for
about a year, so any existing Fedora perf package should be a valid way to
test.

[Justin Forbes (via Email Bridge)]

From: Justin Forbes on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1167#note_5967813...

Acked-by: Justin Forbes 
(via approve button)