[PATCH v2 2/4] irqchip/gic-v2, v3: Implement irq_chip->irq_retrigger()

Marc Zyngier
2020-09-03T18:32:55Z

From: Valentin Schneider <valentin.schneider@arm.com>

While digging around IRQCHIP_EOI_IF_HANDLED and irq/resend.c, it has come
to my attention that the IRQ resend situation seems a bit precarious for
the GIC(s).

When marking an IRQ with IRQS_PENDING, handle_fasteoi_irq() will bail out
and issue an irq_eoi(). Should the IRQ in question be re-enabled,
check_irq_resend() will trigger a SW resend, which will go through the flow
handler again and issue *another* irq_eoi() on the *same* IRQ
activation. This is something the GIC spec clearly describes as a bad idea:
any EOI must match a previous ACK.

Implement irq_chip.irq_retrigger() for the GIC chips by setting the GIC
pending bit of the relevant IRQ. After being called by check_irq_resend(),
this will eventually trigger a *new* interrupt which we will handle as usual.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200730170321.31228-2-valentin.schneider@arm.com
---
drivers/irqchip/irq-gic-v3.c | 7 +++++++
drivers/irqchip/irq-gic.c | 6 ++++++
2 files changed, 13 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 324f280ff606..b507bc7c5cda 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -1207,6 +1207,11 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
#define gic_smp_init() do { } while(0)
#endif

+static int gic_retrigger(struct irq_data *data)
+{
+ return !gic_irq_set_irqchip_state(data, IRQCHIP_STATE_PENDING, true);
+}
+
#ifdef CONFIG_CPU_PM
static int gic_cpu_pm_notifier(struct notifier_block *self,
unsigned long cmd, void *v)
@@ -1242,6 +1247,7 @@ static struct irq_chip gic_chip = {
.irq_eoi = gic_eoi_irq,
.irq_set_type = gic_set_type,
.irq_set_affinity = gic_set_affinity,
+ .irq_retrigger = gic_retrigger,
.irq_get_irqchip_state = gic_irq_get_irqchip_state,
.irq_set_irqchip_state = gic_irq_set_irqchip_state,
.irq_nmi_setup = gic_irq_nmi_setup,
@@ -1258,6 +1264,7 @@ static struct irq_chip gic_eoimode1_chip = {
.irq_eoi = gic_eoimode1_eoi_irq,
.irq_set_type = gic_set_type,
.irq_set_affinity = gic_set_affinity,
+ .irq_retrigger = gic_retrigger,
.irq_get_irqchip_state = gic_irq_get_irqchip_state,
.irq_set_irqchip_state = gic_irq_set_irqchip_state,
.irq_set_vcpu_affinity = gic_irq_set_vcpu_affinity,
diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index a27ba2cc1dce..e92ee2b6d7a5 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -347,6 +347,11 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
}
#endif

+static int gic_retrigger(struct irq_data *data)
+{
+ return !gic_irq_set_irqchip_state(data, IRQCHIP_STATE_PENDING, true);
+}
+
static void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
{
u32 irqstat, irqnr;
@@ -417,6 +422,7 @@ static const struct irq_chip gic_chip = {
.irq_unmask = gic_unmask_irq,
.irq_eoi = gic_eoi_irq,
.irq_set_type = gic_set_type,
+ .irq_retrigger = gic_retrigger,
.irq_get_irqchip_state = gic_irq_get_irqchip_state,
.irq_set_irqchip_state = gic_irq_set_irqchip_state,
.flags = IRQCHIP_SET_TYPE_MASKED |
--
2.28.0