On some hardware models (e.g. Dell Studio 1555 laptop) some hardware
related functions (e.g. SMIs) are to be executed on physical cpu 0
only. Instead of open coding such a functionality multiple times in
the kernel add a service function for this purpose. This will enable
the possibility to take special measures in virtualized environments
like Xen, too.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V5: rename and reshuffle parameters of smp_call_on_cpu() as requested by
Peter Zijlstra
test target cpu to be online as requested by Peter Zijlstra
V4: change return value in case of illegal cpu as requested by Peter Zijlstra
make pinning of vcpu an option as suggested by Peter Zijlstra
V2: instead of manipulating the allowed set of cpus use cpu specific
workqueue as requested by Peter Zijlstra
---
include/linux/smp.h | 3 +++
kernel/smp.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
kernel/up.c | 17 +++++++++++++++++
3 files changed, 70 insertions(+)
diff --git a/include/linux/smp.h b/include/linux/smp.h
index c441407..4f1c475 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -196,4 +196,7 @@ extern void arch_enable_nonboot_cpus_end(void);
void smp_setup_processor_id(void);
+int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par,
+ bool phys);
+
#endif /* __LINUX_SMP_H */
diff --git a/kernel/smp.c b/kernel/smp.c
index 9388064..f671948 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -740,3 +740,53 @@ void wake_up_all_idle_cpus(void)
preempt_enable();
}
EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
+
+/**
+ * smp_call_on_cpu - Call a function on a specific cpu
+ *
+ * Used to call a function on a specific cpu and wait for it to return.
+ * Optionally make sure the call is done on a specified physical cpu via vcpu
+ * pinning in order to support virtualized environments.
+ */
+struct smp_call_on_cpu_struct {
+ struct work_struct work;
+ struct completion done;
+ int (*func)(void *);
+ void *data;
+ int ret;
+ int cpu;
+};
+
+static void smp_call_on_cpu_callback(struct work_struct *work)
+{
+ struct smp_call_on_cpu_struct *sscs;
+
+ sscs = container_of(work, struct smp_call_on_cpu_struct, work);
+ if (sscs->cpu >= 0)
+ hypervisor_pin_vcpu(sscs->cpu);
+ sscs->ret = sscs->func(sscs->data);
+ if (sscs->cpu >= 0)
+ hypervisor_pin_vcpu(-1);
+
+ complete(&sscs->done);
+}
+
+int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
+{
+ struct smp_call_on_cpu_struct sscs = {
+ .work = __WORK_INITIALIZER(sscs.work, smp_call_on_cpu_callback),
+ .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
+ .func = func,
+ .data = par,
+ .cpu = phys ? cpu : -1,
+ };
+
+ if (cpu >= nr_cpu_ids || !cpu_online(cpu))
+ return -ENXIO;
+
+ queue_work_on(cpu, system_wq, &sscs.work);
+ wait_for_completion(&sscs.done);
+
+ return sscs.ret;
+}
+EXPORT_SYMBOL_GPL(smp_call_on_cpu);
diff --git a/kernel/up.c b/kernel/up.c
index 3ccee2b..ee81ac9 100644
--- a/kernel/up.c
+++ b/kernel/up.c
@@ -83,3 +83,20 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
preempt_enable();
}
EXPORT_SYMBOL(on_each_cpu_cond);
+
+int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
+{
+ int ret;
+
+ if (cpu != 0)
+ return -ENXIO;
+
+ if (phys)
+ hypervisor_pin_vcpu(0);
+ ret = func(par);
+ if (phys)
+ hypervisor_pin_vcpu(-1);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(smp_call_on_cpu);
--
2.6.6
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