[PATCH v15 17/20] arm64: kdump: implement machine_crash_shutdown()

Geoff Levand
2016-03-14T17:48:01Z

From: AKASHI Takahiro <takahiro.akashi@linaro.org>

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@linaro.org>
---
arch/arm64/include/asm/hardirq.h | 2 +-
arch/arm64/include/asm/kexec.h | 36 ++++++++++++++++++++++++-
arch/arm64/include/asm/smp.h | 5 ++++
arch/arm64/kernel/machine_kexec.c | 55 +++++++++++++++++++++++++++++++++++---
arch/arm64/kernel/smp.c | 56 +++++++++++++++++++++++++++++++++++++++
5 files changed, 149 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/hardirq.h b/arch/arm64/include/asm/hardirq.h
index a57601f..8740297 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 5
+#define NR_IPI 6

typedef struct {
unsigned int __softirq_pending;
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 04744dc..2f089b3 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -30,6 +30,10 @@

#ifndef __ASSEMBLY__

+#ifndef CONFIG_KEXEC_CORE
+#define crash_save_cpu(regs, cpu)
+#endif
+
/**
* crash_setup_regs() - save registers for the panic kernel
*
@@ -40,7 +44,37 @@
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 {
+ __asm__ __volatile__ (
+ "stp x0, x1, [%3, #16 * 0]\n"
+ "stp x2, x3, [%3, #16 * 1]\n"
+ "stp x4, x5, [%3, #16 * 2]\n"
+ "stp x6, x7, [%3, #16 * 3]\n"
+ "stp x8, x9, [%3, #16 * 4]\n"
+ "stp x10, x11, [%3, #16 * 5]\n"
+ "stp x12, x13, [%3, #16 * 6]\n"
+ "stp x14, x15, [%3, #16 * 7]\n"
+ "stp x16, x17, [%3, #16 * 8]\n"
+ "stp x18, x19, [%3, #16 * 9]\n"
+ "stp x20, x21, [%3, #16 * 10]\n"
+ "stp x22, x23, [%3, #16 * 11]\n"
+ "stp x24, x25, [%3, #16 * 12]\n"
+ "stp x26, x27, [%3, #16 * 13]\n"
+ "stp x28, x29, [%3, #16 * 14]\n"
+ "str x30, [%3, #16 * 15]\n"
+ "mov %0, sp\n"
+ "adr %1, 1f\n"
+ "mrs %2, spsr_el1\n"
+ "1:"
+ : "=r" (newregs->sp),
+ "=r" (newregs->pc),
+ "=r" (newregs->pstate)
+ : "r" (&newregs->regs)
+ : "memory"
+ );
+ }
}

#endif /* __ASSEMBLY__ */
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index d9c3d6a..0e42ece 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -69,4 +69,9 @@ extern int __cpu_disable(void);
extern void __cpu_die(unsigned int cpu);
extern void cpu_die(void);

+/*
+ * for crash dump
+ */
+extern void smp_send_crash_stop(void);
+
#endif /* ifndef __ASM_SMP_H */
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 75f6696..8651b27 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -10,6 +10,9 @@
*/

#include <linux/highmem.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
#include <linux/kexec.h>
#include <linux/libfdt_env.h>
#include <linux/of_fdt.h>
@@ -25,6 +28,7 @@
extern const unsigned char arm64_relocate_new_kernel[];
extern const unsigned long arm64_relocate_new_kernel_size;

+bool in_crash_kexec;
static unsigned long kimage_start;

/**
@@ -150,7 +154,7 @@ void machine_kexec(struct kimage *kimage)
phys_addr_t reboot_code_buffer_phys;
void *reboot_code_buffer;

- BUG_ON(num_online_cpus() > 1);
+ BUG_ON((num_online_cpus() > 1) && !WARN_ON(in_crash_kexec));

reboot_code_buffer_phys = page_to_phys(kimage->control_code_page);
reboot_code_buffer = kmap(kimage->control_code_page);
@@ -209,13 +213,58 @@ void machine_kexec(struct kimage *kimage)
* relocation is complete.
*/

- cpu_soft_restart(is_hyp_mode_available(),
+ cpu_soft_restart(in_crash_kexec ? 0 : is_hyp_mode_available(),
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);
+ }
+}
+
+/**
+ * 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 b1adc51..76402c6cd 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>
@@ -44,6 +45,7 @@
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/cpu_ops.h>
+#include <asm/kexec.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -68,6 +70,7 @@ enum ipi_msg_type {
IPI_RESCHEDULE,
IPI_CALL_FUNC,
IPI_CPU_STOP,
+ IPI_CPU_CRASH_STOP,
IPI_TIMER,
IPI_IRQ_WORK,
};
@@ -625,6 +628,7 @@ 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"),
};
@@ -701,6 +705,28 @@ static void ipi_cpu_stop(unsigned int cpu)
cpu_relax();
}

+static atomic_t waiting_for_crash_ipi;
+
+static void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
+{
+ crash_save_cpu(regs, cpu);
+
+ raw_spin_lock(&stop_lock);
+ pr_debug("CPU%u: stopping\n", cpu);
+ raw_spin_unlock(&stop_lock);
+
+ atomic_dec(&waiting_for_crash_ipi);
+
+ local_irq_disable();
+
+ if (cpu_ops[cpu]->cpu_die)
+ cpu_ops[cpu]->cpu_die(cpu);
+
+ /* just in case */
+ while (1)
+ wfi();
+}
+
/*
* Main handler for inter-processor interrupts
*/
@@ -731,6 +757,12 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
irq_exit();
break;

+ case IPI_CPU_CRASH_STOP:
+ irq_enter();
+ ipi_cpu_crash_stop(cpu, regs);
+ irq_exit();
+ break;
+
#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
case IPI_TIMER:
irq_enter();
@@ -791,6 +823,30 @@ void smp_send_stop(void)
pr_warning("SMP: failed to stop secondary CPUs\n");
}

+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);
+
+ 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_warn("SMP: failed to stop secondary CPUs\n");
+}
+
/*
* not supported here
*/
--
2.5.0