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Peter Anvin" , Ingo Molnar , "Mario Limonciello" , Thomas Gleixner , , Yazen Ghannam CC: Jason Andryuk , , Penny Zheng , Subject: [PATCH 1/2] x86/amd_node: Remove smn_exclusive Date: Thu, 6 Aug 2026 12:01:56 -0400 Message-ID: <20260806160159.230453-2-jason.andryuk@amd.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260806160159.230453-1-jason.andryuk@amd.com> References: <20260806160159.230453-1-jason.andryuk@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-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF0002992C:EE_|PH8PR12MB7110:EE_ X-MS-Office365-Filtering-Correlation-Id: c68f2daa-891e-4f19-753a-08def3d43150 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700016|23010399003|82310400026|376014|11063799006|56012099006|10067099003|6133799003|22082099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(36860700016)(23010399003)(82310400026)(376014)(11063799006)(56012099006)(10067099003)(6133799003)(22082099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: ddIISs/sEv7OkHAzDzBxTa0TjmAi48xFFxcmlS0OmXuccrrttYGUB+xQcMYSSWRhTu8e0AxwDTa0i1LO5QuLZ9gcWaHS1Yfq9zJX7FA66SjqLJ9tKWKaM6NcCI1n79JLAYYNSufuraB/bu/icEpn/Rf5G+NPHFRHLTVsZvaEHZzn+DjR0OTPXnyDaic9p2NdQUm7tUDPheTSdRjUizRfe3lF6hALrL+XRsyF/89tylN5FTwDmUgPqhxLr0kWjoDBUbR4e4YAUPBbnUsJWVwJ8ILMgnKh4tfdgweOra0r1Ke4h6Vv4E30y8xUcw5NaSvsYrlBag+7ldRHo0O/DAliRxblGShFZkenk/WTIRgyXSRHffr0uy6av33Mq0vqEjzeZO3tjkonyeFi9ld0YzTVb3UgATGuodD0rCABJK7kPHzbVy2fHavWPNmxeAOyZQe1 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2026 16:03:01.8705 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c68f2daa-891e-4f19-753a-08def3d43150 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0002992C.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR12MB7110 Content-Type: text/plain; charset="utf-8" amd_smn_read/write() are exported functions around __amd_smn_rw(), so they are always available even if amd_smn_init() fails. smn_exclusive would prevent access __amd_smn_rw(), but it is placed too late. If amd_smn_init() failed, amd_roots is NULL and __amd_smn_rw() will fault over it. Replace smn_exclusive with directly checking amd_roots to avoid the NULL pointer dereference. Fixes: 77466b798d59 ("x86/amd_node: Remove dependency on AMD_NB") Cc: stable@vger.kernel.org Signed-off-by: Jason Andryuk Reviewed-by: Mario Limonciello (AMD) Reviewed-by: Yazen Ghannam --- Fixes is the introduction of amd_roots --- arch/x86/kernel/amd_node.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c index 0be01725a2a4..ea553267e5fa 100644 --- a/arch/x86/kernel/amd_node.c +++ b/arch/x86/kernel/amd_node.c @@ -38,7 +38,6 @@ static struct pci_dev **amd_roots; =20 /* Protect the PCI config register pairs used for SMN. */ static DEFINE_MUTEX(smn_mutex); -static bool smn_exclusive; =20 #define SMN_INDEX_OFFSET 0x60 #define SMN_DATA_OFFSET 0x64 @@ -91,11 +90,11 @@ static int __amd_smn_rw(u8 i_off, u8 d_off, u16 node, u= 32 address, u32 *value, b if (node >=3D amd_num_nodes()) return err; =20 - root =3D amd_roots[node]; - if (!root) + if (!amd_roots) return err; =20 - if (!smn_exclusive) + root =3D amd_roots[node]; 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Peter Anvin" , Ingo Molnar , "Mario Limonciello" , Thomas Gleixner , , Yazen Ghannam CC: Jason Andryuk , , Penny Zheng , Subject: [PATCH 2/2] x86/amd_node: Avoid divide by zero on virtualized systems Date: Thu, 6 Aug 2026 12:01:57 -0400 Message-ID: <20260806160159.230453-3-jason.andryuk@amd.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260806160159.230453-1-jason.andryuk@amd.com> References: <20260806160159.230453-1-jason.andryuk@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-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF00029928:EE_|DS7PR12MB5887:EE_ X-MS-Office365-Filtering-Correlation-Id: d900b567-8328-47b7-9933-08def3d45715 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|36860700016|23010399003|82310400026|56012099006|11063799006|10067099003|22082099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(376014)(36860700016)(23010399003)(82310400026)(56012099006)(11063799006)(10067099003)(22082099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: wmWoHmTWATec0oaMo1O7QKb08supNYEgcaETm4fNmvLBng0DwruYHh+qsqdYLWzTZuIB672aIpkkrRMg0KaBXPD05eJH0nwxXj/IrFMIBs8YRUWhYgxoSFRyVQozcwtJrnDBitxoPLVscc4EI2ZctG2+orJpyU6CSnhg6Nb/YL8hY3i1q2E4EByPCz6/8YjZUhe7CMba4Hrtf0jqrLABe32OGLhdh2ACVssrXCjdavFOaqmGTQyeZ8B9/gv61aGp+VvpBt7BYQexkPf8cq27oEN33SSWw1k2ux3+MIyGLKquZMVA0GQdXVjp98+DzaGv7oaTyWCYKYUP0ZA3DjOZ5JBL1r+hsU3g1VeTdI6VK/vsA1QWMHNATj4XdizAswWfR1rrR2Z7XROk3t9Qk/jL9QcxYOzmflWNVXQTtKVdwoj+h/5bJk16leMrleYvWk6h X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2026 16:04:05.2404 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d900b567-8328-47b7-9933-08def3d45715 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF00029928.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB5887 Content-Type: text/plain; charset="utf-8" On a virtualized system, the number of nodes does not have a relationship to the number of roots. A Xen PVH dom0 can calculate roots_per_node as 0, which crashes with a divide by zero in: if (count++ % roots_per_node) On a virtualized system, default the value to 1. The issue is seen with Xen, but it could affect other systems. Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching") Cc: stable@vger.kernel.org Signed-off-by: Jason Andryuk --- X86_FEATURE_XENPV is only for PV, but this is observed with a PVH dom0. --- arch/x86/kernel/amd_node.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c index ea553267e5fa..c5025e5291b6 100644 --- a/arch/x86/kernel/amd_node.c +++ b/arch/x86/kernel/amd_node.c @@ -286,6 +286,11 @@ static int __init amd_smn_init(void) return -ENOMEM; =20 roots_per_node =3D num_roots / num_nodes; + if (roots_per_node =3D=3D 0) { + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + pr_err(FW_BUG "Error detecting roots per node.\n"); + roots_per_node =3D 1; + } =20 count =3D 0; node =3D 0; --=20 2.55.0