On Wed, Jul 13, 2016 at 10:32:39AM +0100, Suzuki K Poulose wrote:

On 12/07/16 06:05, AKASHI Takahiro wrote:

quoted

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 <redacted>
---
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           | 64 +++++++++++++++++++++++++++++++++++++++
5 files changed, 160 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"
+
+			/* 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 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));

	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);
+	}
+}
+
+/**
+ * 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 62ff3c0..66923db 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

@@ -726,6 +728,7 @@ 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"),

@@ -800,6 +803,30 @@ 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
+

quoted

+	/* just in case */
+	while (1)
+		wfi();

You could use cpu_park_loop() (defined in asm/smp.h) here instead,
which also includes wfe();

Yes, sure.

-Takahiro AKASHI

Suzuki