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To: Michael Ellerman , Thomas Gleixner Cc: Tyrel Datwyler , Michal Suchanek , "Nysal Jan K.A" , Nicholas Piggin , Christophe Leroy , "Naveen N. Rao" , Peter Zijlstra , Laurent Dufour , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] cpu/SMT: Enable SMT only if a core is online Date: Thu, 13 Jun 2024 00:20:37 +0530 Message-ID: <20240612185046.1826891-2-nysal@linux.ibm.com> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240612185046.1826891-1-nysal@linux.ibm.com> References: <20240612185046.1826891-1-nysal@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: _FymjdG9hxQu0ljped2JCYQ1pRpx8xOv X-Proofpoint-ORIG-GUID: h2VSBv1c2klquPJqT3PB7zSTLNv1gZW4 Content-Transfer-Encoding: quoted-printable X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-12_08,2024-06-12_02,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 spamscore=0 adultscore=0 mlxlogscore=999 impostorscore=0 suspectscore=0 clxscore=1015 bulkscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2405170001 definitions=main-2406120131 Content-Type: text/plain; charset="utf-8" From: "Nysal Jan K.A" If a core is offline then enabling SMT should not online CPUs of this core. By enabling SMT, what is intended is either changing the SMT value from "off" to "on" or setting the SMT level (threads per core) from a lower to higher value. On PowerPC the ppc64_cpu utility can be used, among other things, to perform the following functions: ppc64_cpu --cores-on # Get the number of online cores ppc64_cpu --cores-on=3DX # Put exactly X cores online ppc64_cpu --offline-cores=3DX[,Y,...] # Put specified cores offline ppc64_cpu --smt=3D{on|off|value} # Enable, disable or change SMT level If the user has decided to offline certain cores, enabling SMT should not online CPUs in those cores. This patch fixes the issue and changes the behaviour as described, by introducing an arch specific function topology_is_core_online(). It is currently implemented only for PowerPC. Fixes: 73c58e7e1412 ("powerpc: Add HOTPLUG_SMT support") Reported-by: Tyrel Datwyler Closes: https://groups.google.com/g/powerpc-utils-devel/c/wrwVzAAnRlI/m/5KJ= SoqP4BAAJ Signed-off-by: Nysal Jan K.A --- kernel/cpu.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 563877d6c28b..73c4a6f98c4a 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2676,6 +2676,16 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) return ret; } =20 +/** + * Check if the core a CPU belongs to is online + */ +#if !defined(topology_is_core_online) +static inline bool topology_is_core_online(unsigned int cpu) +{ + return true; +} +#endif + int cpuhp_smt_enable(void) { int cpu, ret =3D 0; @@ -2686,7 +2696,7 @@ 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)) + if (!cpu_smt_thread_allowed(cpu) || !topology_is_core_online(cpu)) continue; 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Wed, 12 Jun 2024 18:51:55 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C7FAE20040; Wed, 12 Jun 2024 18:51:52 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CEB832004B; Wed, 12 Jun 2024 18:51:49 +0000 (GMT) Received: from li-80eaad4c-2afd-11b2-a85c-af8123d033e3.ibm.com (unknown [9.124.218.62]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 12 Jun 2024 18:51:49 +0000 (GMT) From: "Nysal Jan K.A." To: Michael Ellerman , Thomas Gleixner Cc: Tyrel Datwyler , Michal Suchanek , "Nysal Jan K.A" , Nicholas Piggin , Christophe Leroy , "Naveen N. Rao" , Peter Zijlstra , Laurent Dufour , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] powerpc/topology: Check if a core is online Date: Thu, 13 Jun 2024 00:20:38 +0530 Message-ID: <20240612185046.1826891-3-nysal@linux.ibm.com> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240612185046.1826891-1-nysal@linux.ibm.com> References: <20240612185046.1826891-1-nysal@linux.ibm.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-TM-AS-GCONF: 00 X-Proofpoint-GUID: y0CmASwOnchMM_lNxM3pTCqYDpQRyUjC X-Proofpoint-ORIG-GUID: 7A2i1_wFaeyJnh6LWP4SYwqr0LtVLDaj X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-12_09,2024-06-12_02,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 phishscore=0 bulkscore=0 mlxlogscore=986 impostorscore=0 spamscore=0 malwarescore=0 suspectscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2405170001 definitions=main-2406120131 Content-Type: text/plain; charset="utf-8" From: "Nysal Jan K.A" topology_is_core_online() checks if the core a CPU belongs to is online. The core is online if at least one of the sibling CPUs is online. The first CPU of an online core is also online in the common case, so this should be fairly quick. Signed-off-by: Nysal Jan K.A --- arch/powerpc/include/asm/topology.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm= /topology.h index f4e6f2dd04b7..16bacfe8c7a2 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -145,6 +145,7 @@ static inline int cpu_to_coregroup_id(int cpu) =20 #ifdef CONFIG_HOTPLUG_SMT #include +#include #include =20 static inline bool topology_is_primary_thread(unsigned int cpu) @@ -156,6 +157,18 @@ static inline bool topology_smt_thread_allowed(unsigne= d int cpu) { return cpu_thread_in_core(cpu) < cpu_smt_num_threads; } + +#define topology_is_core_online topology_is_core_online +static inline bool topology_is_core_online(unsigned int cpu) +{ + int i, first_cpu =3D cpu_first_thread_sibling(cpu); + + for (i =3D first_cpu; i < first_cpu + threads_per_core; ++i) { + if (cpu_online(i)) + return true; + } + return false; +} #endif =20 #endif /* __KERNEL__ */ --=20 2.35.3