powerpc/powernv: process all OPAL event interrupts with kopald

Using irq_work for processing OPAL event interrupts is not necessary.
irq_work is typically used to schedule work from NMI context, a
softirq may be more appropriate. However OPAL events are not
particularly performance or latency critical, so they can all be
invoked by kopald.

This patch removes the irq_work queueing, and instead wakes up
kopald when there is an event to be processed. kopald processes
interrupts individually, enabling irqs and calling cond_resched
between each one to minimise latencies.

Event handlers themselves should still use threaded handlers,
workqueues, etc. as necessary to avoid high interrupts-off latencies
within any single interrupt.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 11 insertions, 12 deletions

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 48fbb41af5d1..0d539c661748 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -540,21 +540,15 @@ int opal_hmi_exception_early(struct pt_regs *regs)
 /* HMI exception handler called in virtual mode during check_irq_replay. */
 int opal_handle_hmi_exception(struct pt_regs *regs)
 {
-	s64 rc;
-	__be64 evt = 0;
-
 	/*
 	 * Check if HMI event is available.
-	 * if Yes, then call opal_poll_events to pull opal messages and
-	 * process them.
+	 * if Yes, then wake kopald to process them.
 	 */
 	if (!local_paca->hmi_event_available)
 		return 0;
 
 	local_paca->hmi_event_available = 0;
-	rc = opal_poll_events(&evt);
-	if (rc == OPAL_SUCCESS && evt)
-		opal_handle_events(be64_to_cpu(evt));
+	opal_wake_poller();
 
 	return 1;
 }
@@ -757,14 +751,19 @@ static void __init opal_imc_init_dev(void)
 static int kopald(void *unused)
 {
 	unsigned long timeout = msecs_to_jiffies(opal_heartbeat) + 1;
-	__be64 events;
 
 	set_freezable();
 	do {
 		try_to_freeze();
-		opal_poll_events(&events);
-		opal_handle_events(be64_to_cpu(events));
-		schedule_timeout_interruptible(timeout);
+
+		opal_handle_events();
+
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (opal_have_pending_events())
+			__set_current_state(TASK_RUNNING);
+		else
+			schedule_timeout(timeout);
+
 	} while (!kthread_should_stop());
 
 	return 0;