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 <swarren@nvidia.com> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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@ -88,4 +88,7 @@ static inline u32 mpidr_hash_size(void)
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{
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return 1 << mpidr_hash.bits;
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}
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extern int platform_can_cpu_hotplug(void);
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#endif
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@ -15,6 +15,7 @@
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#include <asm/mmu_context.h>
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#include <asm/cacheflush.h>
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#include <asm/mach-types.h>
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#include <asm/smp_plat.h>
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#include <asm/system_misc.h>
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extern const unsigned char relocate_new_kernel[];
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@ -38,6 +39,14 @@ int machine_kexec_prepare(struct kimage *image)
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__be32 header;
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int i, err;
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/*
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* Validate that if the current HW supports SMP, then the SW supports
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* and implements CPU hotplug for the current HW. If not, we won't be
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* able to kexec reliably, so fail the prepare operation.
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*/
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if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug())
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return -EINVAL;
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/*
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* No segment at default ATAGs address. try to locate
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* a dtb using magic.
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@ -134,10 +143,13 @@ void machine_kexec(struct kimage *image)
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unsigned long reboot_code_buffer_phys;
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void *reboot_code_buffer;
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if (num_online_cpus() > 1) {
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pr_err("kexec: error: multiple CPUs still online\n");
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return;
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}
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/*
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* This can only happen if machine_shutdown() failed to disable some
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* CPU, and that can only happen if the checks in
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* machine_kexec_prepare() were not correct. If this fails, we can't
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* reliably kexec anyway, so BUG_ON is appropriate.
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*/
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BUG_ON(num_online_cpus() > 1);
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page_list = image->head & PAGE_MASK;
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@ -145,6 +145,16 @@ int boot_secondary(unsigned int cpu, struct task_struct *idle)
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return -ENOSYS;
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}
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int platform_can_cpu_hotplug(void)
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{
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#ifdef CONFIG_HOTPLUG_CPU
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if (smp_ops.cpu_kill)
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return 1;
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#endif
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return 0;
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static void percpu_timer_stop(void);
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