[PATCH v2] riscv: print hartid on bringup

Yunhui Cui
2025-03-03T08:34:37Z

Firmware randomly releases cores, so CPU numbers don't linearly map
to hartids. When the system has an exception, we care more about hartids.
Adding "dyndbg="file smpboot.c +p" loglevel=8" to the cmdline can output
the hartid.

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
---
arch/riscv/kernel/smp.c | 2 ++
arch/riscv/kernel/smpboot.c | 4 ++++
2 files changed, 6 insertions(+)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index d58b5e751286..e650dec44817 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -48,6 +48,8 @@ EXPORT_SYMBOL_GPL(__cpuid_to_hartid_map);
void __init smp_setup_processor_id(void)
{
cpuid_to_hartid_map(0) = boot_cpu_hartid;
+
+ pr_info("Booting Linux on hartid %lu\n", boot_cpu_hartid);
}

static DEFINE_PER_CPU_READ_MOSTLY(int, ipi_dummy_dev);
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index e36d20205bd7..601a321e0f17 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -231,6 +231,10 @@ asmlinkage __visible void smp_callin(void)
riscv_ipi_enable();

numa_add_cpu(curr_cpuid);
+
+ pr_debug("CPU%u: Booted secondary hartid %lu\n", curr_cpuid,
+ cpuid_to_hartid_map(curr_cpuid));
+
set_cpu_online(curr_cpuid, true);

/*
--
2.39.2