From nobody Mon Sep 29 21:14:10 2025 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 5F03BC3F6B0 for ; Mon, 15 Aug 2022 23:09:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239303AbiHOXJQ (ORCPT ); Mon, 15 Aug 2022 19:09:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353145AbiHOXHR (ORCPT ); Mon, 15 Aug 2022 19:07:17 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 401761423EE; Mon, 15 Aug 2022 12:59:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id A7294CE12C1; Mon, 15 Aug 2022 19:59:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EBBBC433C1; Mon, 15 Aug 2022 19:59:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660593559; bh=LVHA3YzYWEMPoW5ZgxNE0Ccb4/VJ6WQwYu7SWqFJdg4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kN3kpXkiNwb6SjPq6wtXPCoU1dDf2GkoBOsggcc4f4qOY06hVlv06IMck93YBObnm cxcF3ejTvkS3J8jN9qYWyHyi1ialOBNs5ktM4FrFrS8MBfeT8usCrapsTyPRpgMwyI yqBaGaY3W58VfgQk2C1oO83EZ6wSTrsLWozhFkxU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , Mark Rutland , Alexey Budankov , linux-arm-kernel@lists.infradead.org, German Gomez , Anshuman Khandual , Suzuki K Poulose , Sasha Levin Subject: [PATCH 5.19 0288/1157] drivers/perf: arm_spe: Fix consistency of SYS_PMSCR_EL1.CX Date: Mon, 15 Aug 2022 19:54:04 +0200 Message-Id: <20220815180451.138467006@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180439.416659447@linuxfoundation.org> References: <20220815180439.416659447@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Anshuman Khandual [ Upstream commit 92f2b8bafa3d6e89c750e9d301a8b7ab76aaa8b6 ] The arm_spe_pmu driver will enable SYS_PMSCR_EL1.CX in order to add CONTEXT packets into the traces, if the owner of the perf event runs with required capabilities i.e CAP_PERFMON or CAP_SYS_ADMIN via perfmon_capable() helper. The value of this bit is computed in the arm_spe_event_to_pmscr() function but the check for capabilities happens in the pmu event init callback i.e arm_spe_pmu_event_init(). This suggests that the value of the CX bit should remain consistent for the duration of the perf session. However, the function arm_spe_event_to_pmscr() may be called later during the event start callback i.e arm_spe_pmu_start() when the "current" process is not the owner of the perf session, hence the CX bit setting is currently not consistent. One way to fix this, is by caching the required value of the CX bit during the initialization of the PMU event, so that it remains consistent for the duration of the session. It uses currently unused 'event->hw.flags' element to cache perfmon_capable() value, which can be referred during event start callback to compute SYS_PMSCR_EL1.CX. This ensures consistent availability of context packets in the trace as per event owner capabilities. Drop BIT(SYS_PMSCR_EL1_CX_SHIFT) check in arm_spe_pmu_event_init(), because now CX bit cannot be set in arm_spe_event_to_pmscr() with perfmon_capable() disabled. Cc: Will Deacon Cc: Mark Rutland Cc: Alexey Budankov Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Fixes: d5d9696b0380 ("drivers/perf: Add support for ARMv8.2 Statistical Pro= filing Extension") Reported-by: German Gomez Signed-off-by: Anshuman Khandual Reviewed-by: Suzuki K Poulose Link: https://lore.kernel.org/r/20220714061302.2715102-1-anshuman.khandual@= arm.com Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- drivers/perf/arm_spe_pmu.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c index db670b265897..b65a7d9640e1 100644 --- a/drivers/perf/arm_spe_pmu.c +++ b/drivers/perf/arm_spe_pmu.c @@ -39,6 +39,24 @@ #include #include =20 +/* + * Cache if the event is allowed to trace Context information. + * This allows us to perform the check, i.e, perfmon_capable(), + * in the context of the event owner, once, during the event_init(). + */ +#define SPE_PMU_HW_FLAGS_CX BIT(0) + +static void set_spe_event_has_cx(struct perf_event *event) +{ + if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && perfmon_capable()) + event->hw.flags |=3D SPE_PMU_HW_FLAGS_CX; +} + +static bool get_spe_event_has_cx(struct perf_event *event) +{ + return !!(event->hw.flags & SPE_PMU_HW_FLAGS_CX); +} + #define ARM_SPE_BUF_PAD_BYTE 0 =20 struct arm_spe_pmu_buf { @@ -272,7 +290,7 @@ static u64 arm_spe_event_to_pmscr(struct perf_event *ev= ent) if (!attr->exclude_kernel) reg |=3D BIT(SYS_PMSCR_EL1_E1SPE_SHIFT); =20 - if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && perfmon_capable()) + if (get_spe_event_has_cx(event)) reg |=3D BIT(SYS_PMSCR_EL1_CX_SHIFT); =20 return reg; @@ -709,10 +727,10 @@ static int arm_spe_pmu_event_init(struct perf_event *= event) !(spe_pmu->features & SPE_PMU_FEAT_FILT_LAT)) return -EOPNOTSUPP; =20 + set_spe_event_has_cx(event); reg =3D arm_spe_event_to_pmscr(event); if (!perfmon_capable() && (reg & (BIT(SYS_PMSCR_EL1_PA_SHIFT) | - BIT(SYS_PMSCR_EL1_CX_SHIFT) | BIT(SYS_PMSCR_EL1_PCT_SHIFT)))) return -EACCES; =20 --=20 2.35.1