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Peter Anvin" Subject: [RFC PATCH v3 01/13] lib/sbm: Introduce helpers for architectures to configure LLC properties Date: Thu, 1 Oct 2026 19:28:37 +0000 Message-ID: <20261001192849.74788-2-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261001192849.74788-1-kprateek.nayak@amd.com> References: <20261001192849.74788-1-kprateek.nayak@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: 8bit Content-Type: text/plain X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF00020E61:EE_|DSAPR12MB520039:EE_ X-MS-Office365-Filtering-Correlation-Id: c9ae57e6-60ff-4e1c-9735-08df1ff25ed0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|7416014|376014|23010399003|1800799024|82310400026|18002099003|22082099003|56012099006|6133799003|10067099003|921020|11063799006; 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)(36860700016)(7416014)(376014)(23010399003)(1800799024)(82310400026)(18002099003)(22082099003)(56012099006)(6133799003)(10067099003)(921020)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 6+aPjeg5tsJq2fE8EE3r+9d7rTkIvfD2CgCC1+SLCLiAiL3ELz/v0elyK/kMeoNzgH2W9eXQrT+qFcV+ZbeSHGEWETwR0ZUZCQVOB97W+kNRga0WJQes/KoK8g+/+c6ODg66wPk3tL6Zeokmdg1oYzgqtmDKXuRNZQk2CdBhSnZrcg1WterlQgsD/kxBIJD77KK7EBbqPNt/crTF8y+cy1XFK5XVXLHOZI9H43np8cdSuNTDuZuuuq/ZyJBezwCpSan8AuNvhPeoSBnk30qqFyJ0lVYqGiCJH/VtyNM3EC0Rfsz2bRDfnpIeTX+vZLeASDHiITdcz9LNH+I6OkmSDLUuXesWQnxsKU4yMvWAY4GnRammKZf8Rxl069B2cA+p3NMDQuP9D3b8o8h0yU2gUYD+BOGHplN3uLjTEwibAYr63RBBeiKoRhgrdnmeIjyv X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Oct 2026 19:29:54.2739 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c9ae57e6-60ff-4e1c-9735-08df1ff25ed0 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: BL6PEPF00020E61.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DSAPR12MB520039 Subsequent commits will add arch/ hooks to configure the sparsebitmask (sbm) topology - number of sbm instance and the maximum CPUs that a single instance can represent. Introduce sbm_set_topology() that helps architectures configure the sbm topology. Also add arch_sbm_cpu_instance_id() which will be used to map CPUs to the sbm instances during init to keep CPUs on the same instance on the same sbm leaf. Individual arch/ users will be added one at a time in the subsequent commits. Signed-off-by: K Prateek Nayak --- include/linux/sbm.h | 8 ++++++++ lib/Makefile | 2 +- lib/sbm.c | 27 +++++++++++++++++++++++++++ 3 files changed, 36 insertions(+), 1 deletion(-) create mode 100644 include/linux/sbm.h create mode 100644 lib/sbm.c diff --git a/include/linux/sbm.h b/include/linux/sbm.h new file mode 100644 index 000000000000..adac12ed233a --- /dev/null +++ b/include/linux/sbm.h @@ -0,0 +1,8 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_SBM_H +#define _LINUX_SBM_H + +int arch_sbm_cpu_instance_id(int cpu); +void sbm_set_topology(int num_instances, int max_threads_per_instance); + +#endif /* _LINUX_SBM_H */ diff --git a/lib/Makefile b/lib/Makefile index dfab958327c5..7776330f5b25 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -40,7 +40,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ earlycpio.o seq_buf.o siphash.o dec_and_lock.o \ nmi_backtrace.o win_minmax.o memcat_p.o \ - buildid.o objpool.o iomem_copy.o sys_info.o + buildid.o objpool.o iomem_copy.o sys_info.o sbm.o lib-$(CONFIG_UNION_FIND) += union_find.o lib-$(CONFIG_PRINTK) += dump_stack.o diff --git a/lib/sbm.c b/lib/sbm.c new file mode 100644 index 000000000000..82280e3306de --- /dev/null +++ b/lib/sbm.c @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include +#include +#include + +static int sbm_max_threads_per_instance = -1; +static int sbm_num_instance = -1; + +/* + * In absence of an arch definition, consider all CPUs to + * belong to the same sbm instance. + */ +int __weak arch_sbm_cpu_instance_id(int cpu) +{ + return 0; +} + +void __init sbm_set_topology(int num_instances, int max_threads_per_instance) +{ + sbm_max_threads_per_instance = max_threads_per_instance; + sbm_num_instance = num_instances; + + pr_info("sbm topology set to %d instance(s) with a maximum of %d thread(s) per instance\n", + sbm_num_instance, + sbm_max_threads_per_instance); +} + -- 2.34.1