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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BN3PEPF0000B372.mail.protection.outlook.com (10.167.243.169) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8272.0 via Frontend Transport; Tue, 10 Dec 2024 09:35:27 +0000 Received: from BLR-L-RBANGORI.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Tue, 10 Dec 2024 03:35:21 -0600 From: Ravi Bangoria To: , , CC: , , , , , , , , , , , , , , , , , , Subject: [PATCH v3 02/10] perf/amd/ibs: Remove pointless sample period check Date: Tue, 10 Dec 2024 09:34:41 +0000 Message-ID: <20241210093449.1662-3-ravi.bangoria@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241210093449.1662-1-ravi.bangoria@amd.com> References: <20241210093449.1662-1-ravi.bangoria@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B372:EE_|CY8PR12MB7338:EE_ X-MS-Office365-Filtering-Correlation-Id: d9c57a2b-cd40-4ece-9b11-08dd18fdfaff X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|36860700013|82310400026; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Dec 2024 09:35:27.2701 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d9c57a2b-cd40-4ece-9b11-08dd18fdfaff X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B372.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7338 Content-Type: text/plain; charset="utf-8" Valid perf event sample period value for IBS PMUs (Fetch and Op both) is limited to multiple of 0x10. perf_ibs_init() has this check: if (!event->attr.sample_freq && hwc->sample_period & 0x0f) return -EINVAL; But it's broken since hwc->sample_period will always be 0 when event->attr.sample_freq is 0 (irrespective of event->attr.freq value.) One option to fix this is to change the condition: - if (!event->attr.sample_freq && hwc->sample_period & 0x0f) + if (!event->attr.freq && hwc->sample_period & 0x0f) However, that will break all userspace tools which have been using IBS event with sample_period not multiple of 0x10. Another option is to remove the condition altogether and mask lower nibble _silently_, same as what current code is inadvertently doing. I'm preferring this approach as it keeps the existing behavior. Acked-by: Namhyung Kim Signed-off-by: Ravi Bangoria --- arch/x86/events/amd/ibs.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c index 4ca8006d2221..bd8919e7c3b1 100644 --- a/arch/x86/events/amd/ibs.c +++ b/arch/x86/events/amd/ibs.c @@ -307,13 +307,8 @@ static int perf_ibs_init(struct perf_event *event) if (config & perf_ibs->cnt_mask) /* raw max_cnt may not be set */ return -EINVAL; - if (!event->attr.sample_freq && hwc->sample_period & 0x0f) - /* - * lower 4 bits can not be set in ibs max cnt, - * but allowing it in case we adjust the - * sample period to set a frequency. - */ - return -EINVAL; + + /* Silently mask off lower nibble. IBS hw mandates it. */ hwc->sample_period &=3D ~0x0FULL; if (!hwc->sample_period) hwc->sample_period =3D 0x10; --=20 2.43.0