[PATCH 1/2] genirq: Allow an interrupt to be marked as 'naked'

Marc Zyngier
2020-11-01T13:14:49Z

Some interrupts (such as the rescheduling IPI) rely on not going through
the irq_enter()/irq_exit() calls. To distinguish such interrupts, add
a new IRQ flag that allows the low-level handling code to sidestep the
enter()/exit() calls.

Only the architecture code is expected to use this. It will do the wrong
thing on normal interrupts.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
include/linux/irq.h | 4 +++-
kernel/irq/debugfs.c | 1 +
kernel/irq/irqdesc.c | 17 ++++++++++++-----
kernel/irq/settings.h | 7 +++++++
4 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index c54365309e97..af5ba7336925 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -72,6 +72,7 @@ enum irqchip_irq_state;
* mechanism and from core side polling.
* IRQ_DISABLE_UNLAZY - Disable lazy irq disable
* IRQ_HIDDEN - Don't show up in /proc/interrupts
+ * IRQ_NAKED - Bypass irq_enter()/irq_exit()
*/
enum {
IRQ_TYPE_NONE = 0x00000000,
@@ -99,13 +100,14 @@ enum {
IRQ_IS_POLLED = (1 << 18),
IRQ_DISABLE_UNLAZY = (1 << 19),
IRQ_HIDDEN = (1 << 20),
+ IRQ_NAKED = (1 << 21),
};

#define IRQF_MODIFY_MASK \
(IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID | \
- IRQ_IS_POLLED | IRQ_DISABLE_UNLAZY | IRQ_HIDDEN)
+ IRQ_IS_POLLED | IRQ_DISABLE_UNLAZY | IRQ_HIDDEN | IRQ_NAKED)

#define IRQ_NO_BALANCING_MASK (IRQ_PER_CPU | IRQ_NO_BALANCING)

diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index e4cff358b437..e031d6afc0f8 100644
--- a/kernel/irq/debugfs.c
+++ b/kernel/irq/debugfs.c
@@ -140,6 +140,7 @@ static const struct irq_bit_descr irqdesc_states[] = {
BIT_MASK_DESCR(_IRQ_IS_POLLED),
BIT_MASK_DESCR(_IRQ_DISABLE_UNLAZY),
BIT_MASK_DESCR(_IRQ_HIDDEN),
+ BIT_MASK_DESCR(_IRQ_NAKED),
};

static const struct irq_bit_descr irqdesc_istates[] = {
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 1a7723604399..c08a1c19d061 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -667,10 +667,9 @@ int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq,
{
struct pt_regs *old_regs = set_irq_regs(regs);
unsigned int irq = hwirq;
+ struct irq_desc *desc;
int ret = 0;

- irq_enter();
-
#ifdef CONFIG_IRQ_DOMAIN
if (lookup)
irq = irq_find_mapping(domain, hwirq);
@@ -680,14 +679,22 @@ int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq,
* Some hardware gives randomly wrong interrupts. Rather
* than crashing, do something sensible.
*/
- if (unlikely(!irq || irq >= nr_irqs)) {
+ desc = irq_to_desc(irq);
+ if (unlikely(!desc || irq >= nr_irqs)) {
ack_bad_irq(irq);
ret = -EINVAL;
+ goto out;
+ }
+
+ if (unlikely(irq_settings_is_naked(desc))) {
+ generic_handle_irq_desc(desc);
} else {
- generic_handle_irq(irq);
+ irq_enter();
+ generic_handle_irq_desc(desc);
+ irq_exit();
}

- irq_exit();
+out:
set_irq_regs(old_regs);
return ret;
}
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 403378b9947b..587e67f9c302 100644
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -18,6 +18,7 @@ enum {
_IRQ_IS_POLLED = IRQ_IS_POLLED,
_IRQ_DISABLE_UNLAZY = IRQ_DISABLE_UNLAZY,
_IRQ_HIDDEN = IRQ_HIDDEN,
+ _IRQ_NAKED = IRQ_NAKED,
_IRQF_MODIFY_MASK = IRQF_MODIFY_MASK,
};

@@ -33,6 +34,7 @@ enum {
#define IRQ_IS_POLLED GOT_YOU_MORON
#define IRQ_DISABLE_UNLAZY GOT_YOU_MORON
#define IRQ_HIDDEN GOT_YOU_MORON
+#define IRQ_NAKED GOT_YOU_MORON
#undef IRQF_MODIFY_MASK
#define IRQF_MODIFY_MASK GOT_YOU_MORON

@@ -174,3 +176,8 @@ static inline bool irq_settings_is_hidden(struct irq_desc *desc)
{
return desc->status_use_accessors & _IRQ_HIDDEN;
}
+
+static inline bool irq_settings_is_naked(struct irq_desc *desc)
+{
+ return desc->status_use_accessors & _IRQ_NAKED;
+}
--
2.28.0