Commit 2103f6cb authored by Stephen Warren's avatar Stephen Warren Committed by Russell King
Browse files

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: default avatarStephen Warren <swarren@nvidia.com>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 00efaa02

arch/arm/include/asm/smp_plat.h

+3 −0
Original line number Diff line number Diff line
@@ -88,4 +88,7 @@ static inline u32 mpidr_hash_size(void) 
{

	return 1 << mpidr_hash.bits;

}



extern int platform_can_cpu_hotplug(void);



#endif

arch/arm/kernel/machine_kexec.c

+16 −4
Original line number Diff line number Diff line
@@ -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;

arch/arm/kernel/smp.c

+10 −0
Original line number Diff line number Diff line
@@ -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);

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