[PATCH v2 2/6] genirq: Allow an interrupt to be marked as 'raw'

Marc Zyngier
2020-11-24T14:15:41Z

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. Note that this is a band-aid until we can
move to some more correct infrastructure (such as kernel/entry/common.c).

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
include/linux/irq.h | 2 ++
kernel/irq/Kconfig | 3 +++
kernel/irq/debugfs.c | 1 +
kernel/irq/irqdesc.c | 17 ++++++++++++-----
kernel/irq/settings.h | 15 +++++++++++++++
5 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index c55f218d5b61..605ba5949255 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_RAW - Skip tick management and irqtime accounting
*/
enum {
IRQ_TYPE_NONE = 0x00000000,
@@ -99,6 +100,7 @@ enum {
IRQ_IS_POLLED = (1 << 18),
IRQ_DISABLE_UNLAZY = (1 << 19),
IRQ_HIDDEN = (1 << 20),
+ IRQ_RAW = (1 << 21),
};

#define IRQF_MODIFY_MASK \
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index 164a031cfdb6..ae9b13d5ee91 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -109,6 +109,9 @@ config GENERIC_IRQ_MATRIX_ALLOCATOR
config GENERIC_IRQ_RESERVATION_MODE
bool

+config ARCH_WANTS_IRQ_RAW
+ bool
+
# Support forced irq threading
config IRQ_FORCED_THREADING
bool
diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index e4cff358b437..f53475d88072 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_RAW),
};

static const struct irq_bit_descr irqdesc_istates[] = {
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 1a7723604399..f5beee546a6f 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)) {
+ if (unlikely(!irq || irq >= nr_irqs || !(desc = irq_to_desc(irq)))) {
ack_bad_irq(irq);
ret = -EINVAL;
+ goto out;
+ }
+
+ if (IS_ENABLED(CONFIG_ARCH_WANTS_IRQ_RAW) &&
+ unlikely(irq_settings_is_raw(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 51acdf43eadc..0033d459fdac 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_RAW = IRQ_RAW,
_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_RAW GOT_YOU_MORON
#undef IRQF_MODIFY_MASK
#define IRQF_MODIFY_MASK GOT_YOU_MORON

@@ -180,3 +182,16 @@ static inline bool irq_settings_is_hidden(struct irq_desc *desc)
{
return desc->status_use_accessors & _IRQ_HIDDEN;
}
+
+static inline bool irq_settings_is_raw(struct irq_desc *desc)
+{
+ if (IS_ENABLED(CONFIG_ARCH_WANTS_IRQ_RAW))
+ return desc->status_use_accessors & _IRQ_RAW;
+
+ /*
+ * Using IRQ_RAW on architectures that don't expect it is
+ * likely to be wrong.
+ */
+ WARN_ON_ONCE(1);
+ return false;
+}
--
2.28.0