irqchip/gic, gic-v3: Make SGIs use handle_percpu_devid_irq()

handle_percpu_devid_fasteoi_ipi() states:

 * The biggest difference with the IRQ version is that the interrupt is
 * EOIed early, as the IPI could result in a context switch, and we need to
 * make sure the IPI can fire again

All that can actually happen scheduler-wise within the handling of an IPI
is the raising of TIF_NEED_RESCHED (and / or folding thereof into
preempt_count); see scheduler_ipi() or sched_ttwu_pending() for instance.

Said flag / preempt_count is evaluated some time later before returning to
whatever context was interrupted, and this gates a call to
preempt_schedule_irq() (arm64_preempt_schedule_irq() in arm64).

Per the above, SGI's do not need a different handler than PPI's, so make
them use the same (handle_percpu_devid_irq).
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201109094121.29975-2-valentin.schneider@arm.com

drivers/irqchip/irq-gic-v3.c

@@ -1302,12 +1302,6 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
 
 	switch (__get_intid_range(hw)) {
 	case SGI_RANGE:
-		irq_set_percpu_devid(irq);
-		irq_domain_set_info(d, irq, hw, chip, d->host_data,
-				    handle_percpu_devid_fasteoi_ipi,
-				    NULL, NULL);
-		break;
-
 	case PPI_RANGE:
 	case EPPI_RANGE:
 		irq_set_percpu_devid(irq);

drivers/irqchip/irq-gic.c

@@ -1005,13 +1005,7 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
 	struct irq_data *irqd = irq_desc_get_irq_data(irq_to_desc(irq));
 
 	switch (hw) {
-	case 0 ... 15:
-		irq_set_percpu_devid(irq);
-		irq_domain_set_info(d, irq, hw, &gic->chip, d->host_data,
-				    handle_percpu_devid_fasteoi_ipi,
-				    NULL, NULL);
-		break;
-	case 16 ... 31:
+	case 0 ... 31:
 		irq_set_percpu_devid(irq);
 		irq_domain_set_info(d, irq, hw, &gic->chip, d->host_data,
 				    handle_percpu_devid_irq, NULL, NULL);