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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 BN2PEPF00004FBD.mail.protection.outlook.com (10.167.243.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8398.14 via Frontend Transport; Thu, 30 Jan 2025 19:49:31 +0000 Received: from [127.0.1.1] (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; Thu, 30 Jan 2025 13:49:30 -0600 From: Yazen Ghannam Date: Thu, 30 Jan 2025 19:48:57 +0000 Subject: [PATCH v4 3/3] x86/amd_node: Add support for debugfs access to SMN registers Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-ID: <20250130-wip-x86-amd-nb-cleanup-v4-3-b5cc997e471b@amd.com> References: <20250130-wip-x86-amd-nb-cleanup-v4-0-b5cc997e471b@amd.com> In-Reply-To: <20250130-wip-x86-amd-nb-cleanup-v4-0-b5cc997e471b@amd.com> To: , Mario Limonciello , "Yazen Ghannam" , Suma Hegde , "Naveen Krishna Chatradhi" , Carlos Bilbao , Hans de Goede , =?utf-8?q?Ilpo_J=C3=A4rvinen?= CC: , X-Mailer: b4 0.15-dev-d23a9 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: BN2PEPF00004FBD:EE_|SA0PR12MB7004:EE_ X-MS-Office365-Filtering-Correlation-Id: 80691a9b-99e1-43c6-90ee-08dd416736e1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|376014|82310400026; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jan 2025 19:49:31.3886 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 80691a9b-99e1-43c6-90ee-08dd416736e1 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: BN2PEPF00004FBD.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB7004 From: Mario Limonciello There are certain registers on AMD Zen systems that can only be accessed through SMN. Introduce a new interface that provides debugfs files for accessing SMN. As this introduces the capability for userspace to manipulate the hardware in unpredictable ways, taint the kernel when writing. Include a kernel parameter to enable the debugfs interface. This is intentionally left undocumented to discourage use of the interface. Signed-off-by: Mario Limonciello Signed-off-by: Yazen Ghannam --- Notes: Link: https://lore.kernel.org/20241206161210.163701-17-yazen.ghannam@amd.com =20 v2->v4: * Was left out of v3. * No change. =20 v1->v2: * Use TAINT_CPU_OUT_OF_SPEC. * Add parameter to enable debugfs interface. * Validate node input from user. arch/x86/kernel/amd_node.c | 99 ++++++++++++++++++++++++++++++++++++++++++= ++++ 1 file changed, 99 insertions(+) diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c index ac571948cb35..b670fa85c61b 100644 --- a/arch/x86/kernel/amd_node.c +++ b/arch/x86/kernel/amd_node.c @@ -8,6 +8,7 @@ * Author: Yazen Ghannam */ =20 +#include #include =20 /* @@ -192,6 +193,87 @@ int __must_check amd_smn_hsmp_rdwr(u16 node, u32 addre= ss, u32 *value, bool write } EXPORT_SYMBOL_GPL(amd_smn_hsmp_rdwr); =20 +static struct dentry *debugfs_dir; +static u16 debug_node; +static u32 debug_address; + +static ssize_t smn_node_write(struct file *file, const char __user *userbu= f, + size_t count, loff_t *ppos) +{ + u16 node; + int ret; + + ret =3D kstrtou16_from_user(userbuf, count, 0, &node); + if (ret) + return ret; + + if (node >=3D amd_num_nodes()) + return -ENODEV; + + debug_node =3D node; + return count; +} + +static int smn_node_show(struct seq_file *m, void *v) +{ + seq_printf(m, "0x%08x\n", debug_node); + return 0; +} + +static ssize_t smn_address_write(struct file *file, const char __user *use= rbuf, + size_t count, loff_t *ppos) +{ + int ret; + + ret =3D kstrtouint_from_user(userbuf, count, 0, &debug_address); + if (ret) + return ret; + + return count; +} + +static int smn_address_show(struct seq_file *m, void *v) +{ + seq_printf(m, "0x%08x\n", debug_address); + return 0; +} + +static int smn_value_show(struct seq_file *m, void *v) +{ + u32 val; + int ret; + + ret =3D amd_smn_read(debug_node, debug_address, &val); + if (ret) + return ret; + + seq_printf(m, "0x%08x\n", val); + return 0; +} + +static ssize_t smn_value_write(struct file *file, const char __user *userb= uf, + size_t count, loff_t *ppos) +{ + u32 val; + int ret; + + ret =3D kstrtouint_from_user(userbuf, count, 0, &val); + if (ret) + return ret; + + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + + ret =3D amd_smn_write(debug_node, debug_address, val); + if (ret) + return ret; + + return count; +} + +DEFINE_SHOW_STORE_ATTRIBUTE(smn_node); +DEFINE_SHOW_STORE_ATTRIBUTE(smn_address); +DEFINE_SHOW_STORE_ATTRIBUTE(smn_value); + static int amd_cache_roots(void) { u16 node, num_nodes =3D amd_num_nodes(); @@ -239,6 +321,15 @@ static int reserve_root_config_spaces(void) return 0; } =20 +static bool enable_dfs; + +static int __init amd_smn_enable_dfs(char *str) +{ + enable_dfs =3D true; + return 1; +} +__setup("amd_smn_debugfs_enable", amd_smn_enable_dfs); + static int __init amd_smn_init(void) { int err; @@ -259,6 +350,14 @@ static int __init amd_smn_init(void) if (err) return err; =20 + if (enable_dfs) { + debugfs_dir =3D debugfs_create_dir("amd_smn", arch_debugfs_dir); + + debugfs_create_file("node", 0600, debugfs_dir, NULL, &smn_node_fops); + debugfs_create_file("address", 0600, debugfs_dir, NULL, &smn_address_fop= s); + debugfs_create_file("value", 0600, debugfs_dir, NULL, &smn_value_fops); + } + return 0; } =20 --=20 2.43.0