[PATCH v2 08/11] x86/microcode: Distinguish NMI control path on stop-machine callback

["Chang S. Bae" <chang.seok.bae@intel.com>]

load_cpus_stopped() currently centralizes the stop_machine() callback for
both NMI and NMI-less rendezvous. microcode_update_handler() alone is
enough for the latter.

While the NMI-based rendezvous finally reaches the same update handler,
it requires additional logic to trigger and process NMIs. That machinery
will be replaced by stop-machine facility.

As preparation for that conversion, split the callback path to make
NMI-specific steps explicit and clear. Rename the function to align with
the change.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
V1 -> V2: Rename load_cpus_stopped() (Thomas)
---
 arch/x86/kernel/cpu/microcode/core.c | 30 ++++++++++++----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 651202e6fefb..abd640b1d286 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -532,7 +532,7 @@ void noinstr microcode_offline_nmi_handler(void)
 	wait_for_ctrl();
 }
 
-static noinstr bool microcode_update_handler(void)
+static noinstr int microcode_update_handler(void *unused)
 {
 	unsigned int cpu = raw_smp_processor_id();
 
@@ -548,7 +548,7 @@ static noinstr bool microcode_update_handler(void)
 	touch_nmi_watchdog();
 	instrumentation_end();
 
-	return true;
+	return 0;
 }
 
 /*
@@ -569,19 +569,15 @@ bool noinstr microcode_nmi_handler(void)
 		return false;
 
 	raw_cpu_write(ucode_ctrl.nmi_enabled, false);
-	return microcode_update_handler();
+	return microcode_update_handler(NULL) == 0;
 }
 
-static int load_cpus_stopped(void *unused)
+static int stop_cpu_in_nmi(void *unused)
 {
-	if (microcode_ops->use_nmi) {
-		/* Enable the NMI handler and raise NMI */
-		this_cpu_write(ucode_ctrl.nmi_enabled, true);
-		apic->send_IPI(smp_processor_id(), NMI_VECTOR);
-	} else {
-		/* Just invoke the handler directly */
-		microcode_update_handler();
-	}
+	/* Enable the NMI handler and raise NMI */
+	this_cpu_write(ucode_ctrl.nmi_enabled, true);
+	apic->send_IPI(smp_processor_id(), NMI_VECTOR);
+
 	return 0;
 }
 
@@ -618,13 +614,13 @@ static int load_late_stop_cpus(bool is_safe)
 	 */
 	store_cpu_caps(&prev_info);
 
-	if (microcode_ops->use_nmi)
+	if (microcode_ops->use_nmi) {
 		static_branch_enable_cpuslocked(&microcode_nmi_handler_enable);
-
-	stop_machine_cpuslocked(load_cpus_stopped, NULL, cpu_online_mask);
-
-	if (microcode_ops->use_nmi)
+		stop_machine_cpuslocked(stop_cpu_in_nmi, NULL, cpu_online_mask);
 		static_branch_disable_cpuslocked(&microcode_nmi_handler_enable);
+	} else {
+		stop_machine_cpuslocked(microcode_update_handler, NULL, cpu_online_mask);
+	}
 
 	/* Analyze the results */
 	for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) {
-- 
2.51.0