Unverified Commit 6825c7a8 authored by Atish Patra's avatar Atish Patra Committed by Palmer Dabbelt
Browse files

RISC-V: Add logical CPU indexing for RISC-V 



Currently, both Linux CPU id and hart 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 hart
id 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: default avatarAtish Patra <atish.patra@wdc.com>
Reviewed-by: default avatarAnup Patel <anup@brainfault.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarPalmer Dabbelt <palmer@sifive.com>
parent a37d56fc

arch/riscv/include/asm/smp.h

+23 −1
Original line number Diff line number Diff line
@@ -18,6 +18,13 @@ 
#include <linux/irqreturn.h>

#include <linux/thread_info.h>



#define INVALID_HARTID ULONG_MAX

/*

 * Mapping between linux logical cpu index and hartid.

 */

extern unsigned long __cpuid_to_hartid_map[NR_CPUS];

#define cpuid_to_hartid_map(cpu)    __cpuid_to_hartid_map[cpu]



#ifdef CONFIG_SMP



/* SMP initialization hook for setup_arch */
@@ -29,12 +36,27 @@ 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 riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out);



/*

 * Obtains the hart ID of the currently executing task.  This relies on

 * THREAD_INFO_IN_TASK, but we define that unconditionally.

 */

#define raw_smp_processor_id() (current_thread_info()->cpu)



#endif /* CONFIG_SMP */

#else



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(cpuid_to_hartid_map(0), out);

}



#endif /* CONFIG_SMP */

#endif /* _ASM_RISCV_SMP_H */

arch/riscv/kernel/setup.c

+4 −0
Original line number Diff line number Diff line
@@ -82,6 +82,10 @@ EXPORT_SYMBOL(empty_zero_page); 
/* The lucky hart to first increment this variable will boot the other cores */

atomic_t hart_lottery;



unsigned long __cpuid_to_hartid_map[NR_CPUS] = {

	[0 ... NR_CPUS-1] = INVALID_HARTID

};



#ifdef CONFIG_BLK_DEV_INITRD

static void __init setup_initrd(void)

{

arch/riscv/kernel/smp.c

+19 −0
Original line number Diff line number Diff line
@@ -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 (cpuid_to_hartid_map(i) == hartid)

			return i;



	pr_err("Couldn't find cpu id for hartid [%d]\n", hartid);

	BUG();

	return i;

}



void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out)

{

	int cpu;



	for_each_cpu(cpu, in)

		cpumask_set_cpu(cpuid_to_hartid_map(cpu), out);

}

/* Unsupported */

int setup_profiling_timer(unsigned int multiplier)

{

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