James, Thank you for your review. On Wed, Sep 14, 2016 at 07:09:33PM +0100, James Morse wrote: > 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.akashi at 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()... My comment above might be confusing, but what I want to fake here is "spsr" as pt_regs.pstate is normally set based on spsr_el1. So there is no corresponding field of SPSEL in spsr. > > > + /* 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? Yes, it can be. > > 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... Good catch! I've never noticed that the message was wrong. The line should be changed to: BUG_ON((cpus_are_stuck_in_kernel() || (num_online_cpus() > 1)) && !in_crash_kexec); > > > > 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. This function was once borrowed from arch/arm, then dropped temporarily and revamped based on Marc's comment IIRC. So I would like to defer to Marc. > > > +/** > > + * 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. Yeah, we could merge them along with ipi_cpu_(crash_)stop(). But the resulting code would be quite noisy if each line is switched by "if (in_crash_kexec)." Otherwise, we may have one big "if" like: void smp_send_stop(void) { if (in_crash_kexec) ... else ... } It seems to me that it is not much different from the current code. What do you think? -Takahiro AKASHI > > > + > > /* > > * not supported here > > */ > > > > > Reviewed-by: James Morse <james.morse at arm.com> > > > Thanks, > > James > > >
