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Subject[tip:core/smp] smp: Add function to execute a function synchronously on a CPU
Commit-ID:  df8ce9d78a4e7fbe7ddfd8ccee3ecaaa0013e883
Gitweb: http://git.kernel.org/tip/df8ce9d78a4e7fbe7ddfd8ccee3ecaaa0013e883
Author: Juergen Gross <jgross@suse.com>
AuthorDate: Mon, 29 Aug 2016 08:48:44 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 5 Sep 2016 13:52:39 +0200

smp: Add function to execute a function synchronously on a CPU

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@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Douglas_Warzecha@dell.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akataria@vmware.com
Cc: boris.ostrovsky@oracle.com
Cc: chrisw@sous-sol.org
Cc: david.vrabel@citrix.com
Cc: hpa@zytor.com
Cc: jdelvare@suse.com
Cc: jeremy@goop.org
Cc: linux@roeck-us.net
Cc: pali.rohar@gmail.com
Cc: rusty@rustcorp.com.au
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1472453327-19050-4-git-send-email-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 eccae469..8e0cb7a 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -196,6 +196,9 @@ 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);
+
/* SMP core functions */
int smpcfd_prepare_cpu(unsigned int cpu);
int smpcfd_dead_cpu(unsigned int cpu);
diff --git a/kernel/smp.c b/kernel/smp.c
index 4274ca5..f4f6137 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -725,3 +725,53 @@ 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);
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