From 2103f6cba61a8b8bea3fc1b63661d830a2125e76 Mon Sep 17 00:00:00 2001 From: Stephen Warren Date: Fri, 2 Aug 2013 20:52:49 +0100 Subject: [PATCH] ARM: 7807/1: kexec: validate CPU hotplug support Architectures should fully validate whether kexec is possible as part of machine_kexec_prepare(), so that user-space's kexec_load() operation can report any problems. Performing validation in machine_kexec() itself is too late, since it is not allowed to return. Prior to this patch, ARM's machine_kexec() was testing after-the-fact whether machine_kexec_prepare() was able to disable all but one CPU. Instead, modify machine_kexec_prepare() to validate all conditions necessary for machine_kexec_prepare()'s to succeed. BUG if the validation succeeded, yet disabling the CPUs didn't actually work. Signed-off-by: Stephen Warren Acked-by: "Eric W. Biederman" Signed-off-by: Russell King --- arch/arm/include/asm/smp_plat.h | 3 +++ arch/arm/kernel/machine_kexec.c | 20 ++++++++++++++++---- arch/arm/kernel/smp.c | 10 ++++++++++ 3 files changed, 29 insertions(+), 4 deletions(-) diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h index 6462a72..a252c0b 100644 --- a/arch/arm/include/asm/smp_plat.h +++ b/arch/arm/include/asm/smp_plat.h @@ -88,4 +88,7 @@ static inline u32 mpidr_hash_size(void) { return 1 << mpidr_hash.bits; } + +extern int platform_can_cpu_hotplug(void); + #endif diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c index 4fb074c..d7c82df 100644 --- a/arch/arm/kernel/machine_kexec.c +++ b/arch/arm/kernel/machine_kexec.c @@ -15,6 +15,7 @@ #include #include #include +#include #include extern const unsigned char relocate_new_kernel[]; @@ -39,6 +40,14 @@ int machine_kexec_prepare(struct kimage *image) int i, err; /* + * Validate that if the current HW supports SMP, then the SW supports + * and implements CPU hotplug for the current HW. If not, we won't be + * able to kexec reliably, so fail the prepare operation. + */ + if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug()) + return -EINVAL; + + /* * No segment at default ATAGs address. try to locate * a dtb using magic. */ @@ -134,10 +143,13 @@ void machine_kexec(struct kimage *image) unsigned long reboot_code_buffer_phys; void *reboot_code_buffer; - if (num_online_cpus() > 1) { - pr_err("kexec: error: multiple CPUs still online\n"); - return; - } + /* + * This can only happen if machine_shutdown() failed to disable some + * CPU, and that can only happen if the checks in + * machine_kexec_prepare() were not correct. If this fails, we can't + * reliably kexec anyway, so BUG_ON is appropriate. + */ + BUG_ON(num_online_cpus() > 1); page_list = image->head & PAGE_MASK; diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index c2b4f8f..2dc19349e 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -145,6 +145,16 @@ int boot_secondary(unsigned int cpu, struct task_struct *idle) return -ENOSYS; } +int platform_can_cpu_hotplug(void) +{ +#ifdef CONFIG_HOTPLUG_CPU + if (smp_ops.cpu_kill) + return 1; +#endif + + return 0; +} + #ifdef CONFIG_HOTPLUG_CPU static void percpu_timer_stop(void); -- 2.7.4