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authorStephen Warren <swarren@nvidia.com>2013-08-02 20:52:49 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2013-08-13 20:23:18 +0100
commit2103f6cba61a8b8bea3fc1b63661d830a2125e76 (patch)
treeecc5f6e4df5631932b38e9eb1d8dd7cd8251ed2b /arch/arm/kernel
parent00efaa0250939dc148e2d3104fb3c18395d24a2d (diff)
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>
Diffstat (limited to 'arch/arm/kernel')
-rw-r--r--arch/arm/kernel/machine_kexec.c20
-rw-r--r--arch/arm/kernel/smp.c10
2 files changed, 26 insertions, 4 deletions
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 4fb074c446bf..d7c82df69243 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -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[];
@@ -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 c2b4f8f0be9a..2dc19349eb19 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);