File perf-evsel-don-t-set-exclude_guest-by-default.p... of Package perf.29801

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File perf-evsel-don-t-set-exclude_guest-by-default.patch of Package perf.29801

From: Ravi Bangoria <ravi.bangoria@amd.com>
Subject: perf evsel: Don't set exclude_guest by default
Date: Tue Nov 2 11:01:12 2021 +0530
Git-commit: eb39bf325631f9ae185abd16281079b7b9858737
References: jsc#SLE-24578 (dependent patch)
Signed-off-by: Tony Jones <tonyj@suse.de>

perf evsel: Don't set exclude_guest by default
    
    Perf tool sets exclude_guest by default while calling perf_event_open().
    Because IBS does not have filtering capability, it always gets rejected
    by IBS PMU driver and thus perf falls back to non-precise sampling. Fix
    it by not setting exclude_guest by default on AMD.
    
    Before:
      $ sudo ./perf record -C 0 -vvv true |& grep precise
        precise_ip                       3
      decreasing precise_ip by one (2)
        precise_ip                       2
      decreasing precise_ip by one (1)
        precise_ip                       1
      decreasing precise_ip by one (0)
    
    After:
      $ sudo ./perf record -C 0 -vvv true |& grep precise
        precise_ip                       3
      decreasing precise_ip by one (2)
        precise_ip                       2
    
    Committer notes:
    
    Fixup init to zero for perf_env in older compilers:
    
      arch/x86/util/evsel.c:15:26: error: missing field 'os_release' initializer [-Werror,-Wmissing-field-initializers]
              struct perf_env env = {0};
                                      ^
    
    Committer notes:
    
    Namhyung remarked:
    
      It'd be nice if it can cover explicit "-e cycles:pp" as well.
    
    Ravi clarified:
    
      For explicit :pp modifier, evsel->precise_max does not get set and thus perf
      does not try with different attr->precise_ip values while exclude_guest set.
      So no issue with explicit :pp:
    
        $ sudo ./perf record -C 0 -e cycles:pp -vvv |& grep "precise_ip\|exclude_guest"
          precise_ip                       2
          exclude_guest                    1
          precise_ip                       2
          exclude_guest                    1
        switching off exclude_guest, exclude_host
          precise_ip                       2
        ^C
    
      Also, with :P modifier, evsel->precise_max gets set but exclude_guest does
      not and thus :P also works fine:
    
        $ sudo ./perf record -C 0 -e cycles:P -vvv |& grep "precise_ip\|exclude_guest"
          precise_ip                       3
        decreasing precise_ip by one (2)
          precise_ip                       2
        ^C
    
    Reported-by: Kim Phillips <kim.phillips@amd.com>
    Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
    Acked-by: Namhyung Kim <namhyung@kernel.org>
    Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Ian Rogers <irogers@google.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Link: http://lore.kernel.org/lkml/20211103072112.32312-1-ravi.bangoria@amd.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/arch/x86/util/evsel.c b/tools/perf/arch/x86/util/evsel.c
index 2f733cdc8dbb..ac2899a25b7a 100644
--- a/tools/perf/arch/x86/util/evsel.c
+++ b/tools/perf/arch/x86/util/evsel.c
@@ -1,8 +1,31 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <stdio.h>
+#include <stdlib.h>
 #include "util/evsel.h"
+#include "util/env.h"
+#include "linux/string.h"
 
 void arch_evsel__set_sample_weight(struct evsel *evsel)
 {
 	evsel__set_sample_bit(evsel, WEIGHT_STRUCT);
 }
+
+void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr)
+{
+	struct perf_env env = { .total_mem = 0, } ;
+
+	if (!perf_env__cpuid(&env))
+		return;
+
+	/*
+	 * On AMD, precise cycles event sampling internally uses IBS pmu.
+	 * But IBS does not have filtering capabilities and perf by default
+	 * sets exclude_guest = 1. This makes IBS pmu event init fail and
+	 * thus perf ends up doing non-precise sampling. Avoid it by clearing
+	 * exclude_guest.
+	 */
+	if (env.cpuid && strstarts(env.cpuid, "AuthenticAMD"))
+		attr->exclude_guest = 0;
+
+	free(env.cpuid);
+}
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3cc1f8fcf15c..ec967fb8d7d9 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -294,7 +294,7 @@ static bool perf_event_can_profile_kernel(void)
 	return perf_event_paranoid_check(1);
 }
 
-struct evsel *evsel__new_cycles(bool precise, __u32 type, __u64 config)
+struct evsel *evsel__new_cycles(bool precise __maybe_unused, __u32 type, __u64 config)
 {
 	struct perf_event_attr attr = {
 		.type	= type,
@@ -305,18 +305,16 @@ struct evsel *evsel__new_cycles(bool precise, __u32 type, __u64 config)
 
 	event_attr_init(&attr);
 
-	if (!precise)
-		goto new_event;
-
 	/*
 	 * Now let the usual logic to set up the perf_event_attr defaults
 	 * to kick in when we return and before perf_evsel__open() is called.
 	 */
-new_event:
 	evsel = evsel__new(&attr);
 	if (evsel == NULL)
 		goto out;
 
+	arch_evsel__fixup_new_cycles(&evsel->core.attr);
+
 	evsel->precise_max = true;
 
 	/* use asprintf() because free(evsel) assumes name is allocated */
@@ -1063,6 +1061,10 @@ void __weak arch_evsel__set_sample_weight(struct evsel *evsel)
 	evsel__set_sample_bit(evsel, WEIGHT);
 }
 
+void __weak arch_evsel__fixup_new_cycles(struct perf_event_attr *attr __maybe_unused)
+{
+}
+
 /*
  * The enable_on_exec/disabled value strategy:
  *
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index dcc87c2881b8..3ea687141afa 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -283,6 +283,7 @@ void __evsel__reset_sample_bit(struct evsel *evsel, enum perf_event_sample_forma
 void evsel__set_sample_id(struct evsel *evsel, bool use_sample_identifier);
 
 void arch_evsel__set_sample_weight(struct evsel *evsel);
+void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr);
 
 int evsel__set_filter(struct evsel *evsel, const char *filter);
 int evsel__append_tp_filter(struct evsel *evsel, const char *filter);

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File perf-evsel-don-t-set-exclude_guest-by-default.patch of Package perf.29801

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