From mboxrd@z Thu Jan 1 00:00:00 1970 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 ED7FCC43334 for ; Wed, 15 Jun 2022 17:57:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244925AbiFOR5M (ORCPT ); Wed, 15 Jun 2022 13:57:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235028AbiFOR5M (ORCPT ); Wed, 15 Jun 2022 13:57:12 -0400 Received: from mail-qk1-x72c.google.com (mail-qk1-x72c.google.com [IPv6:2607:f8b0:4864:20::72c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6261D544C9 for ; Wed, 15 Jun 2022 10:57:11 -0700 (PDT) Received: by mail-qk1-x72c.google.com with SMTP id o73so9308074qke.7 for ; Wed, 15 Jun 2022 10:57:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=maine.edu; s=google; h=from:date:to:cc:subject:message-id:mime-version; bh=lUE1wMAUhn3kDY9KTIDAYl8As1JumgEjfydHKTXBoMA=; b=UWiV+IKLfovZ0BMALPQiVyjiWYDSwQjf/lH3EyiJcqf1sGrFa9gWqv1UgYKIEotxDK 9pfzIcBtAQoovKOvqxNUaBKSI1Fg5CEL0GGtA8Tpq3gqQt4haQyD0qeeDfzPxSlzcX9Q rv6g+VqLqiM0sbc03LRWTiXOe5rhouubMjflU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:date:to:cc:subject:message-id:mime-version; bh=lUE1wMAUhn3kDY9KTIDAYl8As1JumgEjfydHKTXBoMA=; b=oDSjnrNPZk9JjjwfF4bQQC+YsSq+mrFgYZqTtwO3+gE9j0PcYs1jJtI2PBRNwNR7ZE 9yKAA61IS7uPdJYlsKn2FRUzqia5a2ihaRdF+LlvJUtIh5u/FkV7ZwSGmQDHHq+/unj/ 7CQcEt3iJP6YJQB7GTClo0MLFxtMf/8chSMJM2ftuHnD5pMJRd9otsKA4HGUjbq9/3Kf N/McRaMfCIKwykO6UVxT5+S9Y76rxZLzkpbd9evX3M7AYZcRGUfLFY+moFI8by/PbexC NZHyTfzrkZfwxXtHM1uEhdi5Yq74+1BJWQznrwQzCCF0JtzWsi1eNHPfjTdFDAMSMXvl 4PZA== X-Gm-Message-State: AJIora9MPC83zKrN2oALmKHQmSZl80FcC8RPGIPFpVGb/NHXX5+IDeqj Bf8etx16NCq5VXb3le6lwx8GKQ== X-Google-Smtp-Source: AGRyM1vMLNv5LCOOU21DkgjrnWPbkBrClGJuiXoZyFYP/yNZz3BJ/0L0FVWKnHb/Puwp1Jk0RvbucQ== X-Received: by 2002:a37:6b47:0:b0:6a7:48d:e64a with SMTP id g68-20020a376b47000000b006a7048de64amr729185qkc.112.1655315830505; Wed, 15 Jun 2022 10:57:10 -0700 (PDT) Received: from macbook-air.local (weaver.eece.maine.edu. [130.111.218.23]) by smtp.gmail.com with ESMTPSA id cc23-20020a05622a411700b00304f98ad3c1sm9327430qtb.29.2022.06.15.10.57.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jun 2022 10:57:09 -0700 (PDT) From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Wed, 15 Jun 2022 13:57:03 -0400 (EDT) To: linux-kernel@vger.kernel.org cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Catalin Marinas , linux-perf-users@vger.kernel.org, Will Deacon , Mark Rutland , Rob Herring Subject: [perf] why is /proc/sys/kernel/perf_user_access ARM64 only? Message-ID: <30d95df2-c3b-b3e3-d65e-c6be0355fb1@maine.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org Just wasted a lot of time tracking down why rdpmc() event reading wasn't working on an ARM64 machine. It turns out ARM64 has added a custom "/proc/sys/kernel/perf_user_access" to control rdpmc access, but only on ARM64. e2012600810c9ded81f6f63a8d04781be3c300ad Why is this ARM64-only? Why isn't this generic perf infrastructure? How is this different from the existing /sys/bus/event_source/devices/cpu/rdpmc tooling? Also, when user events are disabled, why is the ARMv8 PMU not disabling the cap_user_rdpmc bit in the perf mmap() page? rdpmc was trouble before, but now it's an even bigger architecture-dependent mess just trying to figure out if the feature is enabled or not. Vince