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SubjectRe: [PATCH v2 1/3] RISC-V: Add logical CPU indexing for RISC-V
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On 8/30/18 11:03 PM, Christoph Hellwig wrote:
> On Tue, Aug 28, 2018 at 01:36:08AM -0700, Atish Patra 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 | 18 +++++++++++++++++-
>> arch/riscv/kernel/setup.c | 2 ++
>> arch/riscv/kernel/smp.c | 19 +++++++++++++++++++
>> 3 files changed, 38 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
>> index 36016845..a5c257b3 100644
>> --- a/arch/riscv/include/asm/smp.h
>> +++ b/arch/riscv/include/asm/smp.h
>> @@ -22,6 +22,13 @@
>> #include <linux/cpumask.h>
>> #include <linux/irqreturn.h>
>>
>> +#define INVALID_HARTID -1
>> +/*
>> + * Mapping between linux logical cpu index and hartid.
>> + */
>> +extern unsigned long __cpu_logical_map[NR_CPUS];
>> +#define cpu_logical_map(cpu) __cpu_logical_map[cpu]
>
> How about naming this cpuid_to_hardid_map to make things a little
> more obvious?

Sure.
Also shouldn't this be signed given your INVALID_HARTID
> definition above.
>

I don't know what I was thinking after adding INVALID_HARTID. I will fix
this.

>> +static inline int riscv_hartid_to_cpuid(int hartid) { return 0 ; }
>> +static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in,
>> + struct cpumask *out) {
>> + cpumask_set_cpu(cpu_logical_map(0), out);
>> +}
>
> Please use normal coding style even for stubs:
>
> static inline int riscv_hartid_to_cpuid(int hartid)
> {
> return 0;
> }
>
> static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in,
> struct cpumask *out)
> {
> cpumask_set_cpu(cpu_logical_map(0), out);
> }
>
>> +unsigned long __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HARTID };
>
> Please break the line into the usual format:
>


> unsigned long __cpu_logical_map[NR_CPUS] = {
> [0 ... NR_CPUS-1] = INVALID_HARTID,
> };
>
ok.

Regards,
Atish

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