From: Stephen Warren <swarren@xxxxxxxxxx>
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 at nvidia.com>
Acked-by: "Eric W. Biederman" <ebiederm at xmission.com>
---
v2: Fix compilation issue when !CONFIG_HOTPLUG_CPU
I assume I should add this to the ARM patch tracker immediately, since
it's basically been OK'd except for the compilation issue which this
version fixes.
---
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 <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 3a98192..bd1b9e6 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -144,6 +144,16 @@ 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 int platform_cpu_kill(unsigned int cpu)
{
--
1.8.1.5
