[PATCH v2 05/14] x86: Replace cpu_up/down with devcie_online/offline

[Qais Yousef]

The core device API performs extra housekeeping bits that are missing
from directly calling cpu_up/down.

See commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and
serialization during LPM") for an example description of what might go
wrong.

This also prepares to make cpu_up/down a private interface for anything
but the cpu subsystem.

Signed-off-by: Qais Yousef <qais.yousef@xxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Borislav Petkov <bp@xxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
---
 arch/x86/kernel/topology.c | 4 ++--
 arch/x86/mm/mmio-mod.c     | 8 ++++++--
 arch/x86/xen/smp.c         | 4 +++-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index be5bc2e47c71..3b253088615e 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -69,7 +69,7 @@ int _debug_hotplug_cpu(int cpu, int action)
 
 	switch (action) {
 	case 0:
-		ret = cpu_down(cpu);
+		ret = device_offline(get_cpu_device(cpu));
 		if (!ret) {
 			pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu);
 			dev->offline = true;
@@ -78,7 +78,7 @@ int _debug_hotplug_cpu(int cpu, int action)
 			pr_debug("Can't offline CPU%d.\n", cpu);
 		break;
 	case 1:
-		ret = cpu_up(cpu);
+		ret = device_online(get_cpu_device(cpu));
 		if (!ret) {
 			dev->offline = false;
 			kobject_uevent(&dev->kobj, KOBJ_ONLINE);
diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index b8ef8557d4b3..7ec7d05335ce 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -385,13 +385,15 @@ static void enter_uniprocessor(void)
 		pr_notice("Disabling non-boot CPUs...\n");
 	put_online_cpus();
 
+	lock_device_hotplug();
 	for_each_cpu(cpu, downed_cpus) {
-		err = cpu_down(cpu);
+		err = device_offline(get_cpu_device(cpu));
 		if (!err)
 			pr_info("CPU%d is down.\n", cpu);
 		else
 			pr_err("Error taking CPU%d down: %d\n", cpu, err);
 	}
+	unlock_device_hotplug();
 out:
 	if (num_online_cpus() > 1)
 		pr_warning("multiple CPUs still online, may miss events.\n");
@@ -405,13 +407,15 @@ static void leave_uniprocessor(void)
 	if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
 		return;
 	pr_notice("Re-enabling CPUs...\n");
+	lock_device_hotplug();
 	for_each_cpu(cpu, downed_cpus) {
-		err = cpu_up(cpu);
+		err = device_online(get_cpu_device(cpu));
 		if (!err)
 			pr_info("enabled CPU%d.\n", cpu);
 		else
 			pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
 	}
+	unlock_device_hotplug();
 }
 
 #else /* !CONFIG_HOTPLUG_CPU */
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 7a43b2ae19f1..aaa31100a31e 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -128,11 +128,12 @@ void __init xen_smp_cpus_done(unsigned int max_cpus)
 	if (xen_have_vcpu_info_placement)
 		return;
 
+	lock_device_hotplug();
 	for_each_online_cpu(cpu) {
 		if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS)
 			continue;
 
-		rc = cpu_down(cpu);
+		rc = device_offline(get_cpu_device(cpu));
 
 		if (rc == 0) {
 			/*
@@ -145,6 +146,7 @@ void __init xen_smp_cpus_done(unsigned int max_cpus)
 				__func__, cpu, rc);
 		}
 	}
+	unlock_device_hotplug();
 	WARN(count, "%s: brought %d CPUs offline\n", __func__, count);
 }
 
-- 
2.17.1