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Peter Anvin" , Penny Zheng , , References: <20260623211904.3674-1-jason.andryuk@amd.com> <20260623213552.GAajr8ONjXFUnuUOE3@fat_crate.local> Content-Language: en-US From: Jason Andryuk In-Reply-To: <20260623213552.GAajr8ONjXFUnuUOE3@fat_crate.local> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PEPF00000143:EE_|DM4PR12MB6326:EE_ X-MS-Office365-Filtering-Correlation-Id: 6462ae25-73c5-4545-768a-08ded20758ad X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|23010399003|82310400026|1800799024|376014|13003099007|22082099003|18002099003|56012099006|11063799006|4143699003; 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:satlexmb08.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700016)(23010399003)(82310400026)(1800799024)(376014)(13003099007)(22082099003)(18002099003)(56012099006)(11063799006)(4143699003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: iiNoI5z4rZHP6x0U7XF/lEjsI44H29fE4qvKRFPaNlEdpK1eA6M8ZzoANRE/qaonnCmjH0idkr433se/ROM8F4YfnQ9VMtBy2+cLPboy75vwQ0nvZyyUQiAVNGTIoz9NZsCuMvscWHBVSckr2QnkE9uUB7VB57bfrhSrJc/Y4hnhq4focbH5HmZOm6OBUms0DG7UyBqXG0LkKwWxTg1LqXIqx3RQDQNyH3XDjfbl5SZfygpThm0K8yL1omGN2g5nZyshjmRWi5bkDqEhpeQdB5ukJfJIdxcAj59tv3fHgji1Oob7+/TdX5s5A6R0k/G4Q9Uu7uFJVIWvk3ZKpgYjuC2qIJ7FxwVwqbgj085L6HowT2ZgQUU0AAdx4bhS+6dwymIfpQ4nSK8KHpJfr2+E9RoNl/KGzvOpdEnRIhROXBJX7YI/+NGxSNNkwMi9hLyF X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Jun 2026 15:43:32.7024 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6462ae25-73c5-4545-768a-08ded20758ad 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH2PEPF00000143.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6326 On 2026-06-23 17:35, Borislav Petkov wrote: > On Tue, Jun 23, 2026 at 05:19:03PM -0400, Jason Andryuk wrote: >> Xen synthesizes the CPU topology, so the num_nodes and num_roots values >> may be surprising for amd_smn_init(). Specifically: >> >> roots_per_node = num_roots / num_nodes; >> >> may results in roots_per_node == 0 which leads to divide by zero in >> >> count % roots_per_node >> >> As an example, I have a system with a Xen PVH dom0 that reports: >> Found 1 AMD root devices >> Found 2 AMD nodes >> >> Ensure roots_per_node is at least 1 to avoid the divide by zero errors. >> num_nodes are allocated for amd_roots, so roots_per_node = 1 will >> populate all the entries. >> >> Also add a pr_debug() for the number of nodes. >> >> Cc: stable@vger.kernel.org >> Signed-off-by: Jason Andryuk >> --- >> This is an alternative to >> https://lore.kernel.org/xen-devel/20260506055528.476493-2-penny.zheng@amd.com/ >> but it leaves smn available for dom0. > > Does this alternative work too? > > https://lore.kernel.org/r/20260605230949.GBaiNXPZ2ztjVL7DBg@fat_crate.local It boots as dom0, but smn is disabled. Yours: $ journalctl -b | grep -e amd-pmf -e ypervisor Hypervisor detected: Xen HVM amd-pmf AMDI0107:00: error -EINVAL: error in reading from 0x13b102e8 amd-pmf AMDI0107:00: probe with driver amd-pmf failed with error -22 Mine: $ journalctl -b -2 | grep -e amd-pmf -e ypervisor Hypervisor detected: Xen HVM amd-pmf AMDI0107:00: No Smart PC policy present amd-pmf AMDI0107:00: registered PMF device successfully amd-pmc also fails with yours. dom0 is the privileged hardware domain and sees the physical PCI devices. get_next_root() is looking for AMD or Hygon vendor ids, and dom0 will find those. A regular domain (domU) would see QEMU's emulated pci host bridges, which will be Intel. I have wip s0ix support with Xen where dom0 issues the amd-pmc calls to enter s0ix. I'm not sure of all the uses of SMN, but with Xen dom0/hardware domain running most drivers, I think it should be available. Regards, Jason