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Thu, 29 Jun 2023 14:31:54 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A44EE2004D; Thu, 29 Jun 2023 14:31:53 +0000 (GMT) Received: from pomme.tlslab.ibm.com (unknown [9.101.4.33]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 29 Jun 2023 14:31:53 +0000 (GMT) From: Laurent Dufour To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v3 5/9] cpu/SMT: Create topology_smt_thread_allowed() Date: Thu, 29 Jun 2023 16:31:45 +0200 Message-ID: <20230629143149.79073-6-ldufour@linux.ibm.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230629143149.79073-1-ldufour@linux.ibm.com> References: <20230629143149.79073-1-ldufour@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: KxcTcGvIZ6tUIcw1cIql_noGNEavi-_1 X-Proofpoint-ORIG-GUID: BOffcTQBVUqthzI7--mnQjyWUSJhlr7R X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26 definitions=2023-06-29_03,2023-06-27_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 suspectscore=0 impostorscore=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 spamscore=0 bulkscore=0 adultscore=0 clxscore=1015 priorityscore=1501 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2305260000 definitions=main-2306290132 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, dave.hansen@linux.intel.com, linux-kernel@vger.kernel.org, mingo@redhat.com, bp@alien8.de, npiggin@gmail.com, tglx@linutronix.de Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Michael Ellerman Some architectures allows partial SMT states, ie. when not all SMT threads are brought online. To support that, add an architecture helper which checks whether a given CPU is allowed to be brought online depending on how many SMT threads are currently enabled. Since this is only applicable to architecture supporting partial SMT, only these architectures should select the new configuration variable CONFIG_SMT_NUM_THREADS_DYNAMIC. For the other architectures, not supporting the partial SMT states, there is no need to define topology_cpu_smt_allowed(), the generic code assumed that all the threads are allowed or only the primary ones. Call the helper from cpu_smt_enable(), and cpu_smt_allowed() when SMT is enabled, to check if the particular thread should be onlined. Notably, also call it from cpu_smt_disable() if CPU_SMT_ENABLED, to allow offlining some threads to move from a higher to lower number of threads online. Signed-off-by: Michael Ellerman Suggested-by: Thomas Gleixner [ldufour: slightly reword the commit's description] [ldufour: introduce CONFIG_SMT_NUM_THREADS_DYNAMIC] Signed-off-by: Laurent Dufour --- arch/Kconfig | 3 +++ kernel/cpu.c | 24 +++++++++++++++++++++++- 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/arch/Kconfig b/arch/Kconfig index 205fd23e0cad..c69e9c662a87 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -34,6 +34,9 @@ config ARCH_HAS_SUBPAGE_FAULTS config HOTPLUG_SMT bool +config SMT_NUM_THREADS_DYNAMIC + bool + config GENERIC_ENTRY bool diff --git a/kernel/cpu.c b/kernel/cpu.c index e354af92b2b8..29bf310651c6 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -466,9 +466,23 @@ static int __init smt_cmdline_disable(char *str) } early_param("nosmt", smt_cmdline_disable); +/* + * For Archicture supporting partial SMT states check if the thread is allowed. + * Otherwise this has already been checked through cpu_smt_max_threads when + * setting the SMT level. + */ +static inline bool cpu_smt_thread_allowed(unsigned int cpu) +{ +#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC + return topology_smt_thread_allowed(cpu); +#else + return true; +#endif +} + static inline bool cpu_smt_allowed(unsigned int cpu) { - if (cpu_smt_control == CPU_SMT_ENABLED) + if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu)) return true; if (topology_is_primary_thread(cpu)) @@ -2283,6 +2297,12 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) for_each_online_cpu(cpu) { if (topology_is_primary_thread(cpu)) continue; + /* + * Disable can be called with CPU_SMT_ENABLED when changing + * from a higher to lower number of SMT threads per core. + */ + if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu)) + continue; ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE); if (ret) break; @@ -2317,6 +2337,8 @@ int cpuhp_smt_enable(void) /* Skip online CPUs and CPUs on offline nodes */ if (cpu_online(cpu) || !node_online(cpu_to_node(cpu))) continue; + if (!cpu_smt_thread_allowed(cpu)) + continue; ret = _cpu_up(cpu, 0, CPUHP_ONLINE); if (ret) break;