| Message ID | 20240731030126.956210-2-nysal@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 6c17ea1f3eaa330d445ac14a9428402ce4e3055e |
| Headers | show |
| Series | Skip offline cores when enabling SMT on PowerPC | expand |
On 7/31/24 8:31 AM, Nysal Jan K.A. wrote: > From: "Nysal Jan K.A" <nysal@linux.ibm.com> > > 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=X # Put exactly X cores online > ppc64_cpu --offline-cores=X[,Y,...] # Put specified cores offline > ppc64_cpu --smt={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 <tyreld@linux.ibm.com> > Closes: https://groups.google.com/g/powerpc-utils-devel/c/wrwVzAAnRlI/m/5KJSoqP4BAAJ > Signed-off-by: Nysal Jan K.A <nysal@linux.ibm.com> > --- > Documentation/ABI/testing/sysfs-devices-system-cpu | 3 ++- > kernel/cpu.c | 12 +++++++++++- > 2 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu > index 325873385b71..de725ca3be82 100644 > --- a/Documentation/ABI/testing/sysfs-devices-system-cpu > +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu > @@ -562,7 +562,8 @@ Description: Control Symmetric Multi Threading (SMT) > ================ ========================================= > > If control status is "forceoff" or "notsupported" writes > - are rejected. > + are rejected. Note that enabling SMT on PowerPC skips > + offline cores. > > What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias > Date: March 2019 > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 1209ddaec026..b1fd2a3db91a 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -2689,6 +2689,16 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) > return ret; > } > > +/** > + * 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 = 0; > @@ -2699,7 +2709,7 @@ 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; > ret = _cpu_up(cpu, 0, CPUHP_ONLINE); > if (ret) Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
On Wed, Jul 31 2024 at 08:31, Nysal Jan K. A. wrote: > 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 <tyreld@linux.ibm.com> > Closes: https://groups.google.com/g/powerpc-utils-devel/c/wrwVzAAnRlI/m/5KJSoqP4BAAJ > Signed-off-by: Nysal Jan K.A <nysal@linux.ibm.com> Assuming this goes through the PPC tree: Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Michael: If I should route it through my tree, let me know. Thanks, tglx
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 325873385b71..de725ca3be82 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -562,7 +562,8 @@ Description: Control Symmetric Multi Threading (SMT) ================ ========================================= If control status is "forceoff" or "notsupported" writes - are rejected. + are rejected. Note that enabling SMT on PowerPC skips + offline cores. What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias Date: March 2019 diff --git a/kernel/cpu.c b/kernel/cpu.c index 1209ddaec026..b1fd2a3db91a 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2689,6 +2689,16 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) return ret; } +/** + * 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 = 0; @@ -2699,7 +2709,7 @@ 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; ret = _cpu_up(cpu, 0, CPUHP_ONLINE); if (ret)