linux-kernel - [PATCH] tools/perf: Fix perf test 7 Simple expression parser on s390

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Date:   Wed, 24 Nov 2021 10:03:43 +0100
From:   Thomas Richter <tmricht@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, irogers@...gle.com
Cc:     svens@...ux.ibm.com, gor@...ux.ibm.com, sumanthk@...ux.ibm.com,
        hca@...ux.ibm.com, Thomas Richter <tmricht@...ux.ibm.com>
Subject: [PATCH] tools/perf: Fix perf test 7 Simple expression parser on s390

Commit fdf1e29b6118 ("perf expr: Add metric literals for topology.")
fails on s390:
 # ./perf test -Fv 7
   ...
 # FAILED tests/expr.c:173 #num_dies >= #num_packages
   ---- end ----
   Simple expression parser: FAILED!
 #

Investigating this issue leads to these functions:
 build_cpu_topology()
   +--> has_die_topology(void)
        {
           struct utsname uts;

           if (uname(&uts) < 0)
                  return false;
           if (strncmp(uts.machine, "x86_64", 6))
                  return false;
           ....
        }

which always returns false on s390. The caller build_cpu_topology()
checks has_die_topology() return value. On false the
the struct cpu_topology::die_cpu_list is not contructed and has zero
entries. This leads to the failing comparison: #num_dies >= #num_packages.
s390 of course has a positive number of packages.

Fix this by adding s390 architecture to support CPU die list.

Output after:
 # ./perf test -Fv 7
  7: Simple expression parser                                        :
  --- start ---
  division by zero
  syntax error
  ---- end ----
  Simple expression parser: Ok
 #
Cc: Ian Rogers <irogers@...gle.com>
Fixes: fdf1e29b6118 ("perf expr: Add metric literals for topology.")

Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
---
 tools/perf/util/cputopo.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
index 51b429c86f98..aad7a9e6e31b 100644
--- a/tools/perf/util/cputopo.c
+++ b/tools/perf/util/cputopo.c
@@ -165,7 +165,8 @@ static bool has_die_topology(void)
 	if (uname(&uts) < 0)
 		return false;
 
-	if (strncmp(uts.machine, "x86_64", 6))
+	if (strncmp(uts.machine, "x86_64", 6) &&
+	    strncmp(uts.machine, "s390x", 5))
 		return false;
 
 	scnprintf(filename, MAXPATHLEN, DIE_CPUS_FMT,
-- 
2.31.1