From nobody Sun Feb 8 10:50:14 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B75FDEB64DD for ; Tue, 27 Jun 2023 18:29:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231146AbjF0S27 (ORCPT ); Tue, 27 Jun 2023 14:28:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229623AbjF0S25 (ORCPT ); Tue, 27 Jun 2023 14:28:57 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51B14E71 for ; Tue, 27 Jun 2023 11:28:55 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-5704991ea05so65706677b3.1 for ; Tue, 27 Jun 2023 11:28:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1687890534; x=1690482534; h=to:from:subject:mime-version:message-id:date:from:to:cc:subject :date:message-id:reply-to; bh=pCEk4rjcfYTL2DuAl4m74mxfXYI4yN7w7niW6JdDvXw=; b=Cm3bw124FnPJLd/hOVzZkDDEl6NNM4e2Hl/lg4rqzZFObSGD+uZnXFozeYjh0LOYLL kpEDPktwyWqw0Pq7ozb4zkXc9QwiUAW+kmkiYBWTROZNSUezXf+9Rsv9cqOvedHA/I76 ryK1te8HJfEiHohIYLEA69RFYB+bmV+37MNrsT4ebstip6UaYunO7AdrjpaYjflhlpL6 xS8yCJmHsstL8q/t/CDMkfPTjMJAoTgn+5QT+1HYSIFM8haYxKCw/kaL8B2g9p/CpxVE YTZo30pAo3ee7f6jXZWZIPJ6ae6c/EE7RzoncuCGrfwEJ/Jf8K3Ok1ReXADB6GJnX0AF AsKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687890534; x=1690482534; h=to:from:subject:mime-version:message-id:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=pCEk4rjcfYTL2DuAl4m74mxfXYI4yN7w7niW6JdDvXw=; b=EQlU+I10KXD0RBGF1oe8XFe5R9X5QPdCKb0sFz17UkUW8bzeQ7Ep3R9xq6ftiYb3w6 RjwILoTxGrGMfsf+1kN8E0L4L3NR9QSskRWZGpGE4BRIcmg3yyrbi6Zju8jQI+UgbrqJ UdLtxTt40l5Xzblxqb/ajLElw4O1x5/FhmWllHK9CGhcEse2jeQQJ8Sr+dHvfXqWmbdC zxhyyDOizrJF7TW3LGgv2de6+RyuoYJSL6GT025W0jLAbKcWNdw24vnzW5FmGkWEelbF ZFJ2TdEBSSMNldBOaiYpcWSfc8z4RlbEgBLrMV9CvOuNd6pEjAN3mB2aprrLwR2J7PMA s3tg== X-Gm-Message-State: AC+VfDxGwOKZasDs7xkrbdblr0UdMC9qj/kRYd+yjzwlB6dJ93TX0/Wq WhfWhllIIP1adr8fDbpt/eqTu6eYKfu0 X-Google-Smtp-Source: ACHHUZ6wQDXh989UuoDBFM6nLfDD0nRgSuyNK+A4PNTa/4bB+SnOFzM6nso7l0EW6nj0faBVK5sPn3IhC3XE X-Received: from irogers.svl.corp.google.com ([2620:15c:2a3:200:a518:9a69:cf62:b4d9]) (user=irogers job=sendgmr) by 2002:a81:ac08:0:b0:56d:1b6:5360 with SMTP id k8-20020a81ac08000000b0056d01b65360mr13365076ywh.5.1687890534617; Tue, 27 Jun 2023 11:28:54 -0700 (PDT) Date: Tue, 27 Jun 2023 11:28:34 -0700 Message-Id: <20230627182834.117565-1-irogers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.162.gfafddb0af9-goog Subject: [PATCH v1] perf pmus: Add placeholder core PMU From: Ian Rogers To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Kan Liang , James Clark , Suzuki Poulouse , Rob Herring , Ravi Bangoria , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Yang Jihong Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" If loading a core PMU fails, legacy hardware/cache events may segv due to there being no PMU. Create a placeholder empty PMU for this case. This was discussed in: https://lore.kernel.org/lkml/20230614151625.2077-1-yangjihong1@huawei.com/ Reported-by: Yang Jihong Signed-off-by: Ian Rogers Tested-by: Yang Jihong --- tools/perf/util/pmu.c | 25 +++++++++++++++++++++++++ tools/perf/util/pmu.h | 1 + tools/perf/util/pmus.c | 7 ++++++- 3 files changed, 32 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c index 8d5ecd4ff1a9..7f984a7f16ca 100644 --- a/tools/perf/util/pmu.c +++ b/tools/perf/util/pmu.c @@ -928,6 +928,31 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pm= us, int dirfd, const char return NULL; } =20 +/* Creates the PMU when sysfs scanning fails. */ +struct perf_pmu *perf_pmu__create_placeholder_core_pmu(struct list_head *c= ore_pmus) +{ + struct perf_pmu *pmu =3D zalloc(sizeof(*pmu)); + + if (!pmu) + return NULL; + + pmu->name =3D strdup("cpu"); + if (!pmu->name) { + free(pmu); + return NULL; + } + + pmu->is_core =3D true; + pmu->type =3D PERF_TYPE_RAW; + pmu->cpus =3D cpu_map__online(); + + INIT_LIST_HEAD(&pmu->format); + INIT_LIST_HEAD(&pmu->aliases); + INIT_LIST_HEAD(&pmu->caps); + list_add_tail(&pmu->list, core_pmus); + return pmu; +} + void perf_pmu__warn_invalid_formats(struct perf_pmu *pmu) { struct perf_pmu_format *format; diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h index 8807a624e918..203b92860e3c 100644 --- a/tools/perf/util/pmu.h +++ b/tools/perf/util/pmu.h @@ -286,6 +286,7 @@ int perf_pmu__event_source_devices_fd(void); int perf_pmu__pathname_fd(int dirfd, const char *pmu_name, const char *fil= ename, int flags); =20 struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const= char *lookup_name); +struct perf_pmu *perf_pmu__create_placeholder_core_pmu(struct list_head *c= ore_pmus); void perf_pmu__delete(struct perf_pmu *pmu); =20 #endif /* __PMU_H */ diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c index 0866dee3fc62..3cd9de42139e 100644 --- a/tools/perf/util/pmus.c +++ b/tools/perf/util/pmus.c @@ -153,7 +153,12 @@ static void pmu_read_sysfs(bool core_only) =20 closedir(dir); if (core_only) { - read_sysfs_core_pmus =3D true; + if (!list_empty(&core_pmus)) + read_sysfs_core_pmus =3D true; + else { + if (perf_pmu__create_placeholder_core_pmu(&core_pmus)) + read_sysfs_core_pmus =3D true; + } } else { read_sysfs_core_pmus =3D true; read_sysfs_all_pmus =3D true; --=20 2.41.0.162.gfafddb0af9-goog