MIPS: kexec: Make a framework for both jumping and halting on nonboot CPUs

The existing implementation lets machine_kexec() CPU jump to reboot code
buffer, whereas other CPUs to relocated_kexec_smp_wait. The natural way to
bring up an SMP new kernel would be to let CPU0 do it while others being
halted. For those failing to do so, fall back to the jumping method.

Signed-off-by: Dengcheng Zhu <dzhu@wavecomp.com>
[paul.burton@mips.com: Guard kexec_nonboot_cpu_jump with CONFIG_SMP]
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/20570/
Cc: pburton@wavecomp.com
Cc: ralf@linux-mips.org
Cc: linux-mips@linux-mips.org
Cc: rachel.mozes@intel.com

3 files changed, 93 insertions, 8 deletions

diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c
index 4c07a43a3242..2c7288041a99 100644
--- a/arch/mips/kernel/crash.c
+++ b/arch/mips/kernel/crash.c
@@ -46,7 +46,9 @@ static void crash_shutdown_secondary(void *passed_regs)
 
         while (!atomic_read(&kexec_ready_to_reboot))
                 cpu_relax();
-        relocated_kexec_smp_wait(NULL);
+
+        kexec_reboot();
+
         /* NOTREACHED */
 }
 
diff --git a/arch/mips/kernel/machine_kexec.c b/arch/mips/kernel/machine_kexec.c
index 4b3726e4fe3a..14ced77c5ef6 100644
--- a/arch/mips/kernel/machine_kexec.c
+++ b/arch/mips/kernel/machine_kexec.c
@@ -19,15 +19,19 @@ extern const size_t relocate_new_kernel_size;
 extern unsigned long kexec_start_address;
 extern unsigned long kexec_indirection_page;
 
-int (*_machine_kexec_prepare)(struct kimage *) = NULL;
-void (*_machine_kexec_shutdown)(void) = NULL;
-void (*_machine_crash_shutdown)(struct pt_regs *regs) = NULL;
+static unsigned long reboot_code_buffer;
+
 #ifdef CONFIG_SMP
-void (*relocated_kexec_smp_wait) (void *);
+static void (*relocated_kexec_smp_wait)(void *);
+
 atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
 void (*_crash_smp_send_stop)(void) = NULL;
 #endif
 
+int (*_machine_kexec_prepare)(struct kimage *) = NULL;
+void (*_machine_kexec_shutdown)(void) = NULL;
+void (*_machine_crash_shutdown)(struct pt_regs *regs) = NULL;
+
 static void kexec_image_info(const struct kimage *kimage)
 {
         unsigned long i;
@@ -51,10 +55,16 @@ static void kexec_image_info(const struct kimage *kimage)
 int
 machine_kexec_prepare(struct kimage *kimage)
 {
+#ifdef CONFIG_SMP
+        if (!kexec_nonboot_cpu_func())
+                return -EINVAL;
+#endif
+
         kexec_image_info(kimage);
 
         if (_machine_kexec_prepare)
                 return _machine_kexec_prepare(kimage);
+
         return 0;
 }
 
@@ -63,11 +73,41 @@ machine_kexec_cleanup(struct kimage *kimage)
 {
 }
 
+#ifdef CONFIG_SMP
+static void kexec_shutdown_secondary(void *param)
+{
+        int cpu = smp_processor_id();
+
+        if (!cpu_online(cpu))
+                return;
+
+        /* We won't be sent IPIs any more. */
+        set_cpu_online(cpu, false);
+
+        local_irq_disable();
+        while (!atomic_read(&kexec_ready_to_reboot))
+                cpu_relax();
+
+        kexec_reboot();
+
+        /* NOTREACHED */
+}
+#endif
+
 void
 machine_shutdown(void)
 {
         if (_machine_kexec_shutdown)
                 _machine_kexec_shutdown();
+
+#ifdef CONFIG_SMP
+        smp_call_function(kexec_shutdown_secondary, NULL, 0);
+
+        while (num_online_cpus() > 1) {
+                cpu_relax();
+                mdelay(1);
+        }
+#endif
 }
 
 void
@@ -79,12 +119,47 @@ machine_crash_shutdown(struct pt_regs *regs)
                 default_machine_crash_shutdown(regs);
 }
 
-typedef void (*noretfun_t)(void) __noreturn;
+#ifdef CONFIG_SMP
+void kexec_nonboot_cpu_jump(void)
+{
+        local_flush_icache_range((unsigned long)relocated_kexec_smp_wait,
+                                 reboot_code_buffer + relocate_new_kernel_size);
+
+        relocated_kexec_smp_wait(NULL);
+}
+#endif
+
+void kexec_reboot(void)
+{
+        void (*do_kexec)(void) __noreturn;
+
+#ifdef CONFIG_SMP
+        if (smp_processor_id() > 0) {
+                /*
+                 * Instead of cpu_relax() or wait, this is needed for kexec
+                 * smp reboot. Kdump usually doesn't require an smp new
+                 * kernel, but kexec may do.
+                 */
+                kexec_nonboot_cpu();
+
+                /* NOTREACHED */
+        }
+#endif
+
+        /*
+         * Make sure we get correct instructions written by the
+         * machine_kexec() CPU.
+         */
+        local_flush_icache_range(reboot_code_buffer,
+                                 reboot_code_buffer + relocate_new_kernel_size);
+
+        do_kexec = (void *)reboot_code_buffer;
+        do_kexec();
+}
 
 void
 machine_kexec(struct kimage *image)
 {
-        unsigned long reboot_code_buffer;
         unsigned long entry;
         unsigned long *ptr;
 
@@ -128,6 +203,7 @@ machine_kexec(struct kimage *image)
 
         printk("Will call new kernel at %08lx\n", image->start);
         printk("Bye ...\n");
+        /* Make reboot code buffer available to the boot CPU. */
         __flush_cache_all();
 #ifdef CONFIG_SMP
         /* All secondary cpus now may jump to kexec_wait cycle */
@@ -136,5 +212,5 @@ machine_kexec(struct kimage *image)
         smp_wmb();
         atomic_set(&kexec_ready_to_reboot, 1);
 #endif
-        ((noretfun_t) reboot_code_buffer)();
+        kexec_reboot();
 }
diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
index 159e83add4bb..76fae9b79f13 100644
--- a/arch/mips/kernel/smp-bmips.c
+++ b/arch/mips/kernel/smp-bmips.c
@@ -25,6 +25,7 @@
 #include <linux/linkage.h>
 #include <linux/bug.h>
 #include <linux/kernel.h>
+#include <linux/kexec.h>
 
 #include <asm/time.h>
 #include <asm/pgtable.h>
@@ -423,6 +424,9 @@ const struct plat_smp_ops bmips43xx_smp_ops = {
         .cpu_disable            = bmips_cpu_disable,
         .cpu_die                = bmips_cpu_die,
 #endif
+#ifdef CONFIG_KEXEC
+        .kexec_nonboot_cpu      = kexec_nonboot_cpu_jump,
+#endif
 };
 
 const struct plat_smp_ops bmips5000_smp_ops = {
@@ -437,6 +441,9 @@ const struct plat_smp_ops bmips5000_smp_ops = {
         .cpu_disable            = bmips_cpu_disable,
         .cpu_die                = bmips_cpu_die,
 #endif
+#ifdef CONFIG_KEXEC
+        .kexec_nonboot_cpu      = kexec_nonboot_cpu_jump,
+#endif
 };
 
 #endif /* CONFIG_SMP */