On Thu, Jun 01, 2023 at 02:31:51PM -0700, Douglas Anderson wrote:
> From: Sumit Garg <sumit.g...@linaro.org>
>
> Let's use the debug IPI for rounding up CPUs in kgdb. When the debug
> IPI is backed by an NMI (or pseudo NMI) then this will let us debug
> even hard locked CPUs. When the debug IPI isn't backed by an NMI then
> this won't really have any huge benefit but it will still work.
>
> Signed-off-by: Sumit Garg <sumit.g...@linaro.org>
> Signed-off-by: Douglas Anderson <diand...@chromium.org>
> ---
>
> Changes in v9:
> - Remove fallback for when debug IPI isn't available.
> - Renamed "NMI IPI" to "debug IPI" since it might not be backed by NMI.
>
> arch/arm64/kernel/ipi_debug.c | 5 +++++
> arch/arm64/kernel/kgdb.c | 14 ++++++++++++++
> 2 files changed, 19 insertions(+)
This looks fine to me, but I'd feel a bit happier if we had separate SGIs for
the backtrace and the KGDB callback as they're logically unrelated.
Thanks,
Mark.
>
> diff --git a/arch/arm64/kernel/ipi_debug.c b/arch/arm64/kernel/ipi_debug.c
> index 6984ed507e1f..5794894d94f1 100644
> --- a/arch/arm64/kernel/ipi_debug.c
> +++ b/arch/arm64/kernel/ipi_debug.c
> @@ -8,6 +8,7 @@
>
> #include <linux/interrupt.h>
> #include <linux/irq.h>
> +#include <linux/kgdb.h>
> #include <linux/nmi.h>
> #include <linux/smp.h>
>
> @@ -40,6 +41,7 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
> bool exclude_self)
> static irqreturn_t ipi_debug_handler(int irq, void *data)
> {
> irqreturn_t ret = IRQ_NONE;
> + unsigned int cpu = smp_processor_id();
>
> /*
> * NOTE: Just like in arch_trigger_cpumask_backtrace(), we're calling
> @@ -49,6 +51,9 @@ static irqreturn_t ipi_debug_handler(int irq, void *data)
> if (nmi_cpu_backtrace(get_irq_regs()))
> ret = IRQ_HANDLED;
>
> + if (!kgdb_nmicallback(cpu, get_irq_regs()))
> + ret = IRQ_HANDLED;
> +
> return ret;
> }
>
> diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
> index 4e1f983df3d1..9c4c47507cd4 100644
> --- a/arch/arm64/kernel/kgdb.c
> +++ b/arch/arm64/kernel/kgdb.c
> @@ -20,6 +20,8 @@
> #include <asm/patching.h>
> #include <asm/traps.h>
>
> +#include "ipi_debug.h"
> +
> struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
> { "x0", 8, offsetof(struct pt_regs, regs[0])},
> { "x1", 8, offsetof(struct pt_regs, regs[1])},
> @@ -356,3 +358,15 @@ int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
> return aarch64_insn_write((void *)bpt->bpt_addr,
> *(u32 *)bpt->saved_instr);
> }
> +
> +void kgdb_roundup_cpus(void)
> +{
> + struct cpumask mask;
> +
> + cpumask_copy(&mask, cpu_online_mask);
> + cpumask_clear_cpu(raw_smp_processor_id(), &mask);
> + if (cpumask_empty(&mask))
> + return;
> +
> + arm64_debug_ipi(&mask);
> +}
> --
> 2.41.0.rc2.161.g9c6817b8e7-goog
>
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