Re: [PATCH v22 3/8] arm64: kdump: implement machine_crash_shutdown()

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

On Wed, Jul 13, 2016 at 10:32:39AM +0100, Suzuki K Poulose wrote:
> On 12/07/16 06:05, 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@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           | 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
> >+
> 
> 
> >+	/* 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
> 
> 
> 

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