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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 CY4PEPF0000EE3A.mail.protection.outlook.com (10.167.242.14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.6500.27 via Frontend Transport; Fri, 16 Jun 2023 21:22:59 +0000 Received: from BLR-L-DHSRIVAS.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 15.1.2507.23; Fri, 16 Jun 2023 16:22:55 -0500 From: Dheeraj Kumar Srivastava To: , , , , , CC: , , , Dheeraj Kumar Srivastava , "Kishon Vijay Abraham I" , Vasant Hegde Subject: [PATCH v1] x86/apic: Fix kernel panic when "intremap=off" and "x2apic_phys" are set Date: Sat, 17 Jun 2023 02:52:36 +0530 Message-ID: <20230616212236.1389-1-dheerajkumar.srivastava@amd.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.180.168.240] 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: CY4PEPF0000EE3A:EE_|DM4PR12MB5866:EE_ X-MS-Office365-Filtering-Correlation-Id: 4547be4f-d844-4d87-4919-08db6eafdc7e 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: 16 Jun 2023 21:22:59.9559 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4547be4f-d844-4d87-4919-08db6eafdc7e 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: CY4PEPF0000EE3A.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB5866 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" x2APIC mode requires "Interrupt Remapping" to be enabled and the "physical x2apic" driver can be used only when x2APIC mode is enabled. However when "intremap=3Doff" and "x2apic_phys" kernel command line parameters are passed, "physical x2apic" driver is being used even when x2APIC mode is disabled ("intremap=3Doff" disables x2APIC mode). This results in the below kernel panic: unchecked MSR access error: RDMSR from 0x80f at rIP: 0xffffffff87eab4ec (native_read_msr+0xc/0x40) Call Trace: native_apic_msr_read+0x1f/0x30 setup_local_APIC+0x4e/0x380 ? zen_untrain_ret+0x1/0x1 ? enable_IR_x2apic+0xe8/0x250 apic_intr_mode_init+0x4c/0x120 x86_late_time_init+0x28/0x40 start_kernel+0x626/0xa80 x86_64_start_reservations+0x1c/0x30 x86_64_start_kernel+0xbf/0x110 secondary_startup_64_no_verify+0x10b/0x10b This is due to an incorrect conditional check in x2apic_phys_probe(). Fix it here by returning 0 when "x2apic_mode" is not set in x2apic_phys_probe(). This now prevents default_setup_apic_routing() from selecting "physical x2apic" driver. Fixes: 9ebd680bd029 ("x86, apic: Use probe routines to simplify apic select= ion") Reviewed-by: Kishon Vijay Abraham I Reviewed-by: Vasant Hegde Signed-off-by: Dheeraj Kumar Srivastava Reviewed-by: Cyrill Gorcunov Reviewed-by: Thomas Gleixner --- arch/x86/kernel/apic/x2apic_phys.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2ap= ic_phys.c index 6bde05a86b4e..896bc41cb2ba 100644 --- a/arch/x86/kernel/apic/x2apic_phys.c +++ b/arch/x86/kernel/apic/x2apic_phys.c @@ -97,7 +97,10 @@ static void init_x2apic_ldr(void) =20 static int x2apic_phys_probe(void) { - if (x2apic_mode && (x2apic_phys || x2apic_fadt_phys())) + if (!x2apic_mode) + return 0; + + if (x2apic_phys || x2apic_fadt_phys()) return 1; =20 return apic =3D=3D &apic_x2apic_phys; --=20 2.25.1