From 983f12149942a58c66e9db7638a10667aae0d958 Mon Sep 17 00:00:00 2001 From: Jinjie Ruan Date: Sat, 27 Jul 2024 14:34:38 +0800 Subject: [PATCH] RISC-V: Implement kgdb_roundup_cpus() to enable future NMI Roundup Until now, the generic weak kgdb_roundup_cpus() has been used for kgdb on RISCV. A custom one allows to debug CPUs that are stuck with interrupts disabled with NMI support in the future. And using an IPI is better than the generic one since it avoids the potential situation described in the generic kgdb_call_nmi_hook(). As Andrew pointed out, once there is NMI support, we can easily extend this and the CPU backtrace support to use NMIs. After this patch, the kgdb test show that: # echo g > /proc/sysrq-trigger [2]kdb> btc btc: cpu status: Currently on cpu 2 Available cpus: 0-1(-), 2, 3(-) Stack traceback for pid 0 0xffffffff81c13a40 0 0 1 0 - 0xffffffff81c14510 swapper/0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.10.0-g3120273055b6-dirty #51 Hardware name: riscv-virtio,qemu (DT) Call Trace: [] dump_backtrace+0x28/0x30 [] show_stack+0x38/0x44 [] dump_stack_lvl+0x58/0x7a [] dump_stack+0x18/0x20 [] kgdb_cpu_enter+0x682/0x6b2 [] kgdb_nmicallback+0xa0/0xac [] handle_IPI+0x9c/0x120 [] handle_percpu_devid_irq+0xa4/0x1e4 [] generic_handle_domain_irq+0x28/0x36 [] ipi_mux_process+0xe8/0x110 [] imsic_handle_irq+0xf8/0x13a [] generic_handle_domain_irq+0x28/0x36 [] riscv_intc_aia_irq+0x2e/0x40 [] handle_riscv_irq+0x54/0x86 [] call_on_irq_stack+0x32/0x40 Rebased on Ryo Takakura's "RISC-V: Enable IPI CPU Backtrace" patch. Signed-off-by: Jinjie Ruan Reviewed-by: Andrew Jones Link: https://lore.kernel.org/r/20240727063438.886155-1-ruanjinjie@huawei.com Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/smp.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c index 9b047899791ce8..c180a647a30e44 100644 --- a/arch/riscv/kernel/smp.c +++ b/arch/riscv/kernel/smp.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -35,6 +36,7 @@ enum ipi_message_type { IPI_IRQ_WORK, IPI_TIMER, IPI_CPU_BACKTRACE, + IPI_KGDB_ROUNDUP, IPI_MAX }; @@ -115,6 +117,7 @@ void arch_irq_work_raise(void) static irqreturn_t handle_IPI(int irq, void *data) { + unsigned int cpu = smp_processor_id(); int ipi = irq - ipi_virq_base; switch (ipi) { @@ -128,7 +131,7 @@ static irqreturn_t handle_IPI(int irq, void *data) ipi_stop(); break; case IPI_CPU_CRASH_STOP: - ipi_cpu_crash_stop(smp_processor_id(), get_irq_regs()); + ipi_cpu_crash_stop(cpu, get_irq_regs()); break; case IPI_IRQ_WORK: irq_work_run(); @@ -141,8 +144,11 @@ static irqreturn_t handle_IPI(int irq, void *data) case IPI_CPU_BACKTRACE: nmi_cpu_backtrace(get_irq_regs()); break; + case IPI_KGDB_ROUNDUP: + kgdb_nmicallback(cpu, get_irq_regs()); + break; default: - pr_warn("CPU%d: unhandled IPI%d\n", smp_processor_id(), ipi); + pr_warn("CPU%d: unhandled IPI%d\n", cpu, ipi); break; } @@ -209,6 +215,7 @@ static const char * const ipi_names[] = { [IPI_IRQ_WORK] = "IRQ work interrupts", [IPI_TIMER] = "Timer broadcast interrupts", [IPI_CPU_BACKTRACE] = "CPU backtrace interrupts", + [IPI_KGDB_ROUNDUP] = "KGDB roundup interrupts", }; void show_ipi_stats(struct seq_file *p, int prec) @@ -339,3 +346,19 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) { nmi_trigger_cpumask_backtrace(mask, exclude_cpu, riscv_backtrace_ipi); } + +#ifdef CONFIG_KGDB +void kgdb_roundup_cpus(void) +{ + int this_cpu = raw_smp_processor_id(); + int cpu; + + for_each_online_cpu(cpu) { + /* No need to roundup ourselves */ + if (cpu == this_cpu) + continue; + + send_ipi_single(cpu, IPI_KGDB_ROUNDUP); + } +} +#endif