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ARM: 7807/1: kexec: validate CPU hotplug support

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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>
This commit is contained in:
Stephen Warren 2013-08-02 20:52:49 +01:00 • committed by Russell King
commit 2103f6cba6
3 changed files with 29 additions and 4 deletions
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3
arch/arm/include/asm/smp_plat.h
View file

@ -88,4 +88,7 @@ static inline u32 mpidr_hash_size(void)
{
return 1 << mpidr_hash.bits;
}
extern int platform_can_cpu_hotplug(void);
#endif

20
arch/arm/kernel/machine_kexec.c
View file

@ -15,6 +15,7 @@
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/mach-types.h>
#include <asm/smp_plat.h>
#include <asm/system_misc.h>
extern const unsigned char relocate_new_kernel[];
@ -38,6 +39,14 @@ int machine_kexec_prepare(struct kimage *image)
__be32 header;
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;

10
arch/arm/kernel/smp.c
View file

@ -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);