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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BL6PEPF0001AB55.mail.protection.outlook.com (10.167.241.7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.7113.14 via Frontend Transport; Sun, 17 Dec 2023 17:26:34 +0000 Received: from sindhu.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 15.1.2507.34; Sun, 17 Dec 2023 11:26:29 -0600 From: Sandipan Das To: , CC: , , , , , , , , , , , , , , , , Subject: [PATCH 2/3] perf/x86/amd/lbr: Discard erroneous branch entries Date: Sun, 17 Dec 2023 22:55:44 +0530 Message-ID: X-Mailer: git-send-email 2.34.1 In-Reply-To: References: 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: BL6PEPF0001AB55:EE_|DM6PR12MB4941:EE_ X-MS-Office365-Filtering-Correlation-Id: 6f1480ca-f42b-4cab-8c5b-08dbff25518a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Dec 2023 17:26:34.9495 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6f1480ca-f42b-4cab-8c5b-08dbff25518a 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: BL6PEPF0001AB55.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4941 Content-Type: text/plain; charset="utf-8" The Revision Guide for AMD Family 19h Model 10-1Fh processors, found at the link below, declares Erratum 1452 which states that non-branch entries may erroneously be recorded in the Last Branch Record (LBR) stack with the valid and spec bits set. Such entries can be recognized by inspecting bit 61 of the corresponding LastBranchStackToIp register. This bit is currently reserved but if found to be set, the associated branch entry should be discarded. Link: https://bugzilla.kernel.org/attachment.cgi?id=3D305518 Signed-off-by: Sandipan Das Cc: stable@vger.kernel.org --- arch/x86/events/amd/lbr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c index 110e34c59643..43bf2dbcdb82 100644 --- a/arch/x86/events/amd/lbr.c +++ b/arch/x86/events/amd/lbr.c @@ -173,9 +173,11 @@ void amd_pmu_lbr_read(void) =20 /* * Check if a branch has been logged; if valid =3D 0, spec =3D 0 - * then no branch was recorded + * then no branch was recorded; if reserved =3D 1 then an + * erroneous branch was recorded (see erratum 1452) */ - if (!entry.to.split.valid && !entry.to.split.spec) + if ((!entry.to.split.valid && !entry.to.split.spec) || + entry.to.split.reserved) continue; =20 perf_clear_branch_entry_bitfields(br + out); --=20 2.34.1