| Message ID | 20240806085320.63514-2-yangyicong@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Support SMT control on arm64 | expand |
On 06/08/2024 10:53, Yicong Yang wrote: > From: Yicong Yang <yangyicong@hisilicon.com> > > Currently if architectures want to support HOTPLUG_SMT they need to > provide a topology_is_primary_thread() telling the framework which > thread in the SMT cannot offline. However arm64 doesn't have a > restriction on which thread in the SMT cannot offline, a simplest > choice is that just make 1st thread as the "primary" thread. So > just make this as the default implementation in the framework and > let architectures like x86 that have special primary thread to > override this function. IMHO, ARM64 (/ARM), RISCV and PARISC (SMP) use GENERIC_ARCH_TOPOLOGY (and drivers/base/arch_topology.c) so they could share topology_is_primary_thread() also there? [...]
On 2024/8/16 23:54, Dietmar Eggemann wrote: > On 06/08/2024 10:53, Yicong Yang wrote: >> From: Yicong Yang <yangyicong@hisilicon.com> >> >> Currently if architectures want to support HOTPLUG_SMT they need to >> provide a topology_is_primary_thread() telling the framework which >> thread in the SMT cannot offline. However arm64 doesn't have a >> restriction on which thread in the SMT cannot offline, a simplest >> choice is that just make 1st thread as the "primary" thread. So >> just make this as the default implementation in the framework and >> let architectures like x86 that have special primary thread to >> override this function. > > IMHO, ARM64 (/ARM), RISCV and PARISC (SMP) use GENERIC_ARCH_TOPOLOGY > (and drivers/base/arch_topology.c) so they could share > topology_is_primary_thread() also there? > I think yes, if they want to implement HOTPLUG_SMT and don't have a restriction on the primary thread. Thanks.
diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index f4e6f2dd04b7..e0971777f2d9 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -151,6 +151,7 @@ static inline bool topology_is_primary_thread(unsigned int cpu) { return cpu == cpu_first_thread_sibling(cpu); } +#define topology_is_primary_thread topology_is_primary_thread static inline bool topology_smt_thread_allowed(unsigned int cpu) { diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index abe3a8f22cbd..86c077f8ee99 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -219,11 +219,11 @@ static inline bool topology_is_primary_thread(unsigned int cpu) { return cpumask_test_cpu(cpu, cpu_primary_thread_mask); } +#define topology_is_primary_thread topology_is_primary_thread #else /* CONFIG_SMP */ static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } static inline int topology_max_smt_threads(void) { return 1; } -static inline bool topology_is_primary_thread(unsigned int cpu) { return true; } static inline unsigned int topology_amd_nodes_per_pkg(void) { return 1; } #endif /* !CONFIG_SMP */ diff --git a/include/linux/topology.h b/include/linux/topology.h index 52f5850730b3..9c9f6b9f3462 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -240,6 +240,20 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) } #endif +#ifndef topology_is_primary_thread +#define topology_is_primary_thread topology_is_primary_thread +static inline bool topology_is_primary_thread(unsigned int cpu) +{ + /* + * On SMT hotplug the primary thread of the SMT won't be disabled. + * Architectures do have a special primary thread (e.g. x86) need + * to override this function. Otherwise just make the first thread + * in the SMT as the primary thread. + */ + return cpu == cpumask_first(topology_sibling_cpumask(cpu)); +} +#endif + static inline const struct cpumask *cpu_cpu_mask(int cpu) { return cpumask_of_node(cpu_to_node(cpu));