Messages in this thread Patch in this message | | | From | Anup Patel <> | Date | Thu, 16 Aug 2018 09:36:04 +0530 | Subject | Re: [RFC PATCH 1/5] RISC-V: Add logical CPU indexing for RISC-V |
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On Thu, Aug 16, 2018 at 5:26 AM, Atish Patra <atish.patra@wdc.com> wrote: > Currently, both linux cpu id and hardware cpu id are same. > This is not recommended as it will lead to discontinuous cpu > indexing in Linux. Moreover, kdump kernel will run from CPU0 > which would be absent if we follow existing scheme. > > Implement a logical mapping between Linux cpu id and hardware > cpuid to decouple these two. Always mark the boot processor as > cpu0 and all other cpus get the logical cpu id based on their > booting order. > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > --- > arch/riscv/include/asm/smp.h | 17 ++++++++++++++++- > arch/riscv/kernel/setup.c | 2 ++ > arch/riscv/kernel/smp.c | 19 +++++++++++++++++++ > 3 files changed, 37 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h > index 36016845..0763337b 100644 > --- a/arch/riscv/include/asm/smp.h > +++ b/arch/riscv/include/asm/smp.h > @@ -22,6 +22,12 @@ > #include <linux/cpumask.h> > #include <linux/irqreturn.h> > > +/* > + * Mapping between linux logical cpu index and hartid. > + */ > +extern u64 __cpu_logical_map[NR_CPUS]; > +#define cpu_logical_map(cpu) __cpu_logical_map[cpu] > + > #ifdef CONFIG_SMP > > /* SMP initialization hook for setup_arch */ > @@ -33,6 +39,8 @@ void arch_send_call_function_ipi_mask(struct cpumask *mask); > /* Hook for the generic smp_call_function_single() routine. */ > void arch_send_call_function_single_ipi(int cpu); > > +int riscv_hartid_to_cpuid(int hartid); > +void cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out); > /* > * This is particularly ugly: it appears we can't actually get the definition > * of task_struct here, but we need access to the CPU this task is running on. > @@ -41,6 +49,13 @@ void arch_send_call_function_single_ipi(int cpu); > */ > #define raw_smp_processor_id() (*((int*)((char*)get_current() + TASK_TI_CPU))) > > -#endif /* CONFIG_SMP */ > +#else > + > +static inline int riscv_hartid_to_cpuid(int hartid) { return 0 ; } > +static inline void cpuid_to_hartid_mask(const struct cpumask *in, > + struct cpumask *out) { > + cpumask_set_cpu(cpu_logical_map(0), out); > +} > > +#endif /* CONFIG_SMP */ > #endif /* _ASM_RISCV_SMP_H */ > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index db20dc63..e21ed481 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -82,6 +82,8 @@ EXPORT_SYMBOL(empty_zero_page); > /* The lucky hart to first increment this variable will boot the other cores */ > atomic_t hart_lottery; > > +u64 __cpu_logical_map[NR_CPUS];
If hardware IDs are always machine word size then its better to use "unsigned long" in-place of u64.
The __cpu_logical_map[] should be zero initially because zero is a valid hardware ID. Better set all entries to -1 by assigning { -1 } to the array.
Also, I feel __cpu_logical_map[] should be part of smp.c instead of setup.c. Any particular reason for having it in setup.c?
> + > #ifdef CONFIG_BLK_DEV_INITRD > static void __init setup_initrd(void) > { > diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c > index 906fe21e..d55379ee 100644 > --- a/arch/riscv/kernel/smp.c > +++ b/arch/riscv/kernel/smp.c > @@ -38,7 +38,26 @@ enum ipi_message_type { > IPI_MAX > }; > > +int riscv_hartid_to_cpuid(int hartid) > +{ > + int i = -1; > + > + for (i = 0; i < NR_CPUS; i++) > + if (cpu_logical_map(i) == hartid) > + return i; > + > + pr_err("Couldn't find cpu id for hartid [%d]\n", hartid); > + BUG(); > + return i; > +} > > +void cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out)
May be rename cpuid_to_hartid_mask() to riscv_cpuid_to_hartid_mask() for consistency.
> +{ > + int cpu; > + > + for_each_cpu(cpu, in) > + cpumask_set_cpu(cpu_logical_map(cpu), out); > +} > /* Unsupported */ > int setup_profiling_timer(unsigned int multiplier) > { > -- > 2.7.4 >
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