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: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 85d7619eb92726132989400cbd7751ff99c252a6..47fd61dfc89732458113dfd71c84b19d69acaeb6 100644 (file)
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -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 */

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index b2d26d9d8489c8e8b6bba01adee0c573fd6564f8..d5d8611066d56514c7357d30a1265b6445fa58e9 100644 (file)
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -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)
 {

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 906fe21ea21bf3f10db2e460cfe2b4fbd21ac790..0bd48935f886fb87b724d3d45ee29f81d68a3c17 100644 (file)
--- 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 (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)
 {