Hi Akashi,
(CC: Marc who knows how this irqchip wizardry works
Cover letter: https://www.spinics.net/lists/arm-kernel/msg529520.html )
On 07/09/16 05:29, AKASHI Takahiro wrote:
> Primary kernel calls machine_crash_shutdown() to shut down non-boot cpus
> and save registers' status in per-cpu ELF notes before starting crash
> dump kernel. See kernel_kexec().
> Even if not all secondary cpus have shut down, we do kdump anyway.
>
> As we don't have to make non-boot(crashed) cpus offline (to preserve
> correct status of cpus at crash dump) before shutting down, this patch
> also adds a variant of smp_send_stop().
>
> Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
> ---
> arch/arm64/include/asm/hardirq.h | 2 +-
> arch/arm64/include/asm/kexec.h | 41 ++++++++++++++++++++++++-
> arch/arm64/include/asm/smp.h | 2 ++
> arch/arm64/kernel/machine_kexec.c | 56 ++++++++++++++++++++++++++++++++--
> arch/arm64/kernel/smp.c | 63
> +++++++++++++++++++++++++++++++++++++++
> 5 files changed, 159 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/include/asm/hardirq.h
> b/arch/arm64/include/asm/hardirq.h
> index 8740297..1473fc2 100644
> --- a/arch/arm64/include/asm/hardirq.h
> +++ b/arch/arm64/include/asm/hardirq.h
> @@ -20,7 +20,7 @@
> #include <linux/threads.h>
> #include <asm/irq.h>
>
> -#define NR_IPI 6
> +#define NR_IPI 7
>
> typedef struct {
> unsigned int __softirq_pending;
> diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
> index 04744dc..a908958 100644
> --- a/arch/arm64/include/asm/kexec.h
> +++ b/arch/arm64/include/asm/kexec.h
> @@ -40,7 +40,46 @@
> static inline void crash_setup_regs(struct pt_regs *newregs,
> struct pt_regs *oldregs)
> {
> - /* Empty routine needed to avoid build errors. */
> + if (oldregs) {
> + memcpy(newregs, oldregs, sizeof(*newregs));
> + } else {
> + u64 tmp1, tmp2;
> +
> + __asm__ __volatile__ (
> + "stp x0, x1, [%2, #16 * 0]\n"
> + "stp x2, x3, [%2, #16 * 1]\n"
> + "stp x4, x5, [%2, #16 * 2]\n"
> + "stp x6, x7, [%2, #16 * 3]\n"
> + "stp x8, x9, [%2, #16 * 4]\n"
> + "stp x10, x11, [%2, #16 * 5]\n"
> + "stp x12, x13, [%2, #16 * 6]\n"
> + "stp x14, x15, [%2, #16 * 7]\n"
> + "stp x16, x17, [%2, #16 * 8]\n"
> + "stp x18, x19, [%2, #16 * 9]\n"
> + "stp x20, x21, [%2, #16 * 10]\n"
> + "stp x22, x23, [%2, #16 * 11]\n"
> + "stp x24, x25, [%2, #16 * 12]\n"
> + "stp x26, x27, [%2, #16 * 13]\n"
> + "stp x28, x29, [%2, #16 * 14]\n"
> + "mov %0, sp\n"
> + "stp x30, %0, [%2, #16 * 15]\n"
> +
> + "/* faked current PSTATE */\n"
> + "mrs %0, CurrentEL\n"
> + "mrs %1, DAIF\n"
> + "orr %0, %0, %1\n"
> + "mrs %1, NZCV\n"
> + "orr %0, %0, %1\n"
> +
What about SPSEL? While we don't use it, it is correctly preserved for
everything except a CPU that calls panic()...
> + /* pc */
> + "adr %1, 1f\n"
> + "1:\n"
> + "stp %1, %0, [%2, #16 * 16]\n"
> + : "=r" (tmp1), "=r" (tmp2), "+r" (newregs)
> + :
> + : "memory"
> + );
> + }
> }
>
> #endif /* __ASSEMBLY__ */
> diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
> index 0226447..6b0f2c7 100644
> --- a/arch/arm64/include/asm/smp.h
> +++ b/arch/arm64/include/asm/smp.h
> @@ -136,6 +136,8 @@ static inline void cpu_panic_kernel(void)
> */
> bool cpus_are_stuck_in_kernel(void);
>
> +extern void smp_send_crash_stop(void);
> +
> #endif /* ifndef __ASSEMBLY__ */
>
> #endif /* ifndef __ASM_SMP_H */
> diff --git a/arch/arm64/kernel/machine_kexec.c
> b/arch/arm64/kernel/machine_kexec.c
> index bc96c8a..8ac9dba8 100644
> --- a/arch/arm64/kernel/machine_kexec.c
> +++ b/arch/arm64/kernel/machine_kexec.c
> @@ -9,6 +9,9 @@
> * published by the Free Software Foundation.
> */
>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/kernel.h>
> #include <linux/kexec.h>
> #include <linux/smp.h>
>
> @@ -22,6 +25,7 @@
> extern const unsigned char arm64_relocate_new_kernel[];
> extern const unsigned long arm64_relocate_new_kernel_size;
>
> +bool in_crash_kexec;
static?
> static unsigned long kimage_start;
>
> /**
> @@ -148,7 +152,8 @@ void machine_kexec(struct kimage *kimage)
> /*
> * New cpus may have become stuck_in_kernel after we loaded the image.
> */
> - BUG_ON(cpus_are_stuck_in_kernel() || (num_online_cpus() > 1));
> + BUG_ON((cpus_are_stuck_in_kernel() || (num_online_cpus() > 1)) &&
> + !WARN_ON(in_crash_kexec));
In the kdump case, num_online_cpus() is unchanged as ipi_cpu_crash_stop()
doesn't update the online cpu masks, so this WARN_ON always fires. This is
confusing as the 'failed to stop secondary CPUs' message doesn't appear, because
those CPUs did stop, and waiting_for_crash_ipi has the expected value...
>
> reboot_code_buffer_phys = page_to_phys(kimage->control_code_page);
> reboot_code_buffer = phys_to_virt(reboot_code_buffer_phys);
> @@ -200,13 +205,58 @@ void machine_kexec(struct kimage *kimage)
> * relocation is complete.
> */
>
> - cpu_soft_restart(1, reboot_code_buffer_phys, kimage->head,
> + cpu_soft_restart(!in_crash_kexec, reboot_code_buffer_phys, kimage->head,
> kimage_start, 0);
>
> BUG(); /* Should never get here. */
> }
> +static void machine_kexec_mask_interrupts(void)
> +{
> + unsigned int i;
> + struct irq_desc *desc;
> +
> + for_each_irq_desc(i, desc) {
> + struct irq_chip *chip;
> + int ret;
> +
> + chip = irq_desc_get_chip(desc);
> + if (!chip)
> + continue;
> +
> + /*
> + * First try to remove the active state. If this
> + * fails, try to EOI the interrupt.
> + */
> + ret = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
> +
> + if (ret && irqd_irq_inprogress(&desc->irq_data) &&
> + chip->irq_eoi)
> + chip->irq_eoi(&desc->irq_data);
> +
> + if (chip->irq_mask)
> + chip->irq_mask(&desc->irq_data);
> +
> + if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
> + chip->irq_disable(&desc->irq_data);
> + }
> +}
This function is over my head ... I have no idea how this works, I can only
comment that its different to the version under arch/arm
/me adds Marc Z to CC.
> +/**
> + * machine_crash_shutdown - shutdown non-crashing cpus and save registers
> + */
> void machine_crash_shutdown(struct pt_regs *regs)
> {
> - /* Empty routine needed to avoid build errors. */
> + local_irq_disable();
> +
> + in_crash_kexec = true;
> +
> + /* shutdown non-crashing cpus */
> + smp_send_crash_stop();
> +
> + /* for crashing cpu */
> + crash_save_cpu(regs, smp_processor_id());
> + machine_kexec_mask_interrupts();
> +
> + pr_info("Starting crashdump kernel...\n");
> }
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index d93d433..b401b25 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -37,6 +37,7 @@
> #include <linux/completion.h>
> #include <linux/of.h>
> #include <linux/irq_work.h>
> +#include <linux/kexec.h>
>
> #include <asm/alternative.h>
> #include <asm/atomic.h>
> @@ -71,6 +72,7 @@ enum ipi_msg_type {
> IPI_RESCHEDULE,
> IPI_CALL_FUNC,
> IPI_CPU_STOP,
> + IPI_CPU_CRASH_STOP,
> IPI_TIMER,
> IPI_IRQ_WORK,
> IPI_WAKEUP
> @@ -734,6 +736,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string
> = {
> S(IPI_RESCHEDULE, "Rescheduling interrupts"),
> S(IPI_CALL_FUNC, "Function call interrupts"),
> S(IPI_CPU_STOP, "CPU stop interrupts"),
> + S(IPI_CPU_CRASH_STOP, "CPU stop (for crash dump) interrupts"),
> S(IPI_TIMER, "Timer broadcast interrupts"),
> S(IPI_IRQ_WORK, "IRQ work interrupts"),
> S(IPI_WAKEUP, "CPU wake-up interrupts"),
> @@ -808,6 +811,29 @@ static void ipi_cpu_stop(unsigned int cpu)
> cpu_relax();
> }
>
> +#ifdef CONFIG_KEXEC_CORE
> +static atomic_t waiting_for_crash_ipi;
> +#endif
> +
> +static void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
> +{
> +#ifdef CONFIG_KEXEC_CORE
> + crash_save_cpu(regs, cpu);
> +
> + atomic_dec(&waiting_for_crash_ipi);
> +
> + local_irq_disable();
> +
> +#ifdef CONFIG_HOTPLUG_CPU
> + if (cpu_ops[cpu]->cpu_die)
> + cpu_ops[cpu]->cpu_die(cpu);
> +#endif
> +
> + /* just in case */
> + cpu_park_loop();
> +#endif
> +}
> +
> /*
> * Main handler for inter-processor interrupts
> */
> @@ -838,6 +864,15 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
> irq_exit();
> break;
>
> + case IPI_CPU_CRASH_STOP:
> + if (IS_ENABLED(CONFIG_KEXEC_CORE)) {
> + irq_enter();
> + ipi_cpu_crash_stop(cpu, regs);
> +
> + unreachable();
> + }
> + break;
> +
> #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
> case IPI_TIMER:
> irq_enter();
> @@ -910,6 +945,34 @@ void smp_send_stop(void)
> cpumask_pr_args(cpu_online_mask));
> }
>
> +#ifdef CONFIG_KEXEC_CORE
> +void smp_send_crash_stop(void)
> +{
> + cpumask_t mask;
> + unsigned long timeout;
> +
> + if (num_online_cpus() == 1)
> + return;
> +
> + cpumask_copy(&mask, cpu_online_mask);
> + cpumask_clear_cpu(smp_processor_id(), &mask);
> +
> + atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
> +
> + pr_crit("SMP: stopping secondary CPUs\n");
> + smp_cross_call(&mask, IPI_CPU_CRASH_STOP);
> +
> + /* Wait up to one second for other CPUs to stop */
> + timeout = USEC_PER_SEC;
> + while ((atomic_read(&waiting_for_crash_ipi) > 0) && timeout--)
> + udelay(1);
> +
> + if (atomic_read(&waiting_for_crash_ipi) > 0)
> + pr_warning("SMP: failed to stop secondary CPUs %*pbl\n",
> + cpumask_pr_args(cpu_online_mask));
> +}
> +#endif
This is very similar to smp_send_stop() which also has the timeout. Is it
possible to merge them? You could use in_crash_kexec to choose the IPI type.
> +
> /*
> * not supported here
> */
>
Reviewed-by: James Morse <james.mo...@arm.com>
Thanks,
James
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
