From: Michael Ellerman <[email protected]>
Add support for HOTPLUG_SMT, which enables the generic sysfs SMT support
files in /sys/devices/system/cpu/smt, as well as the "nosmt" boot
parameter.
Implement the recently added hooks to allow partial SMT states, allow
any number of threads per core.
Tie the config symbol to HOTPLUG_CPU, which enables it on the major
platforms that support SMT. If there are other platforms that want the
SMT support that can be tweaked in future.
Signed-off-by: Michael Ellerman <[email protected]>
[ldufour: pass current SMT level to cpu_smt_set_num_threads]
[ldufour: remove topology_smt_supported]
[ldufour: remove topology_smt_threads_supported]
[ldufour: select CONFIG_SMT_NUM_THREADS_DYNAMIC]
[ldufour: update kernel-parameters.txt]
Signed-off-by: Laurent Dufour <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 4 ++--
arch/powerpc/Kconfig | 2 ++
arch/powerpc/include/asm/topology.h | 15 +++++++++++++++
arch/powerpc/kernel/smp.c | 8 +++++++-
4 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9e5bab29685f..5efb6c73a928 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3838,10 +3838,10 @@
nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
and disable the IO APIC. legacy for "maxcpus=0".
- nosmt [KNL,S390] Disable symmetric multithreading (SMT).
+ nosmt [KNL,S390,PPC] Disable symmetric multithreading (SMT).
Equivalent to smt=1.
- [KNL,X86] Disable symmetric multithreading (SMT).
+ [KNL,X86,PPC] Disable symmetric multithreading (SMT).
nosmt=force: Force disable SMT, cannot be undone
via the sysfs control file.
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8b955bc7b59f..bacabc3d7f0c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -273,6 +273,8 @@ config PPC
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_VIRT_CPU_ACCOUNTING
select HAVE_VIRT_CPU_ACCOUNTING_GEN
+ select HOTPLUG_SMT if HOTPLUG_CPU
+ select SMT_NUM_THREADS_DYNAMIC
select HUGETLB_PAGE_SIZE_VARIABLE if PPC_BOOK3S_64 && HUGETLB_PAGE
select IOMMU_HELPER if PPC64
select IRQ_DOMAIN
diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
index 8a4d4f4d9749..f4e6f2dd04b7 100644
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -143,5 +143,20 @@ static inline int cpu_to_coregroup_id(int cpu)
#endif
#endif
+#ifdef CONFIG_HOTPLUG_SMT
+#include <linux/cpu_smt.h>
+#include <asm/cputhreads.h>
+
+static inline bool topology_is_primary_thread(unsigned int cpu)
+{
+ return cpu == cpu_first_thread_sibling(cpu);
+}
+
+static inline bool topology_smt_thread_allowed(unsigned int cpu)
+{
+ return cpu_thread_in_core(cpu) < cpu_smt_num_threads;
+}
+#endif
+
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_TOPOLOGY_H */
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 406e6d0ffae3..eb539325dff8 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1087,7 +1087,7 @@ static int __init init_big_cores(void)
void __init smp_prepare_cpus(unsigned int max_cpus)
{
- unsigned int cpu;
+ unsigned int cpu, num_threads;
DBG("smp_prepare_cpus\n");
@@ -1154,6 +1154,12 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
if (smp_ops && smp_ops->probe)
smp_ops->probe();
+
+ // Initalise the generic SMT topology support
+ num_threads = 1;
+ if (smt_enabled_at_boot)
+ num_threads = smt_enabled_at_boot;
+ cpu_smt_set_num_threads(num_threads, threads_per_core);
}
void smp_prepare_boot_cpu(void)
--
2.41.0
Hi Michael,
Le 29/06/2023 à 16:31, Laurent Dufour a écrit :
> From: Michael Ellerman <[email protected]>
>
> Add support for HOTPLUG_SMT, which enables the generic sysfs SMT support
> files in /sys/devices/system/cpu/smt, as well as the "nosmt" boot
> parameter.
>
> Implement the recently added hooks to allow partial SMT states, allow
> any number of threads per core.
>
> Tie the config symbol to HOTPLUG_CPU, which enables it on the major
> platforms that support SMT. If there are other platforms that want the
> SMT support that can be tweaked in future.
>
> Signed-off-by: Michael Ellerman <[email protected]>
> [ldufour: pass current SMT level to cpu_smt_set_num_threads]
> [ldufour: remove topology_smt_supported]
> [ldufour: remove topology_smt_threads_supported]
> [ldufour: select CONFIG_SMT_NUM_THREADS_DYNAMIC]
> [ldufour: update kernel-parameters.txt]
> Signed-off-by: Laurent Dufour <[email protected]>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 4 ++--
> arch/powerpc/Kconfig | 2 ++
> arch/powerpc/include/asm/topology.h | 15 +++++++++++++++
> arch/powerpc/kernel/smp.c | 8 +++++++-
> 4 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 9e5bab29685f..5efb6c73a928 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3838,10 +3838,10 @@
> nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
> and disable the IO APIC. legacy for "maxcpus=0".
>
> - nosmt [KNL,S390] Disable symmetric multithreading (SMT).
> + nosmt [KNL,S390,PPC] Disable symmetric multithreading (SMT).
> Equivalent to smt=1.
>
> - [KNL,X86] Disable symmetric multithreading (SMT).
> + [KNL,X86,PPC] Disable symmetric multithreading (SMT).
> nosmt=force: Force disable SMT, cannot be undone
> via the sysfs control file.
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 8b955bc7b59f..bacabc3d7f0c 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -273,6 +273,8 @@ config PPC
> select HAVE_SYSCALL_TRACEPOINTS
> select HAVE_VIRT_CPU_ACCOUNTING
> select HAVE_VIRT_CPU_ACCOUNTING_GEN
> + select HOTPLUG_SMT if HOTPLUG_CPU
> + select SMT_NUM_THREADS_DYNAMIC
I missed that this list should be kept sorted alphabetically.
Could you fix that when applying the series, or should I send a new
version ?
Thanks,
Laurent.
> select HUGETLB_PAGE_SIZE_VARIABLE if PPC_BOOK3S_64 && HUGETLB_PAGE
> select IOMMU_HELPER if PPC64
> select IRQ_DOMAIN
> diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
> index 8a4d4f4d9749..f4e6f2dd04b7 100644
> --- a/arch/powerpc/include/asm/topology.h
> +++ b/arch/powerpc/include/asm/topology.h
> @@ -143,5 +143,20 @@ static inline int cpu_to_coregroup_id(int cpu)
> #endif
> #endif
>
> +#ifdef CONFIG_HOTPLUG_SMT
> +#include <linux/cpu_smt.h>
> +#include <asm/cputhreads.h>
> +
> +static inline bool topology_is_primary_thread(unsigned int cpu)
> +{
> + return cpu == cpu_first_thread_sibling(cpu);
> +}
> +
> +static inline bool topology_smt_thread_allowed(unsigned int cpu)
> +{
> + return cpu_thread_in_core(cpu) < cpu_smt_num_threads;
> +}
> +#endif
> +
> #endif /* __KERNEL__ */
> #endif /* _ASM_POWERPC_TOPOLOGY_H */
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 406e6d0ffae3..eb539325dff8 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1087,7 +1087,7 @@ static int __init init_big_cores(void)
>
> void __init smp_prepare_cpus(unsigned int max_cpus)
> {
> - unsigned int cpu;
> + unsigned int cpu, num_threads;
>
> DBG("smp_prepare_cpus\n");
>
> @@ -1154,6 +1154,12 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>
> if (smp_ops && smp_ops->probe)
> smp_ops->probe();
> +
> + // Initalise the generic SMT topology support
> + num_threads = 1;
> + if (smt_enabled_at_boot)
> + num_threads = smt_enabled_at_boot;
> + cpu_smt_set_num_threads(num_threads, threads_per_core);
> }
>
> void smp_prepare_boot_cpu(void)