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Subject[RFC PATCH 03/23] genirq: Introduce IRQF_DELIVER_AS_NMI
Date
Certain interrupt controllers (such as APIC) are capable of delivering
interrupts as non-maskable. Likewise, drivers or subsystems (e.g., the
hardlockup detector) might be interested in requesting a non-maskable
interrupt. The new flag IRQF_DELIVER_AS_NMI serves this purpose.

When setting up an interrupt, non-maskable delivery will be set in the
interrupt state data only if supported by the underlying interrupt
controller chips.

Interrupt controller chips can declare that they support non-maskable
delivery by using the new flag IRQCHIP_CAN_DELIVER_AS_NMI.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jacob Pan <jacob.jun.pan@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
include/linux/interrupt.h | 3 +++
include/linux/irq.h | 3 +++
kernel/irq/manage.c | 22 +++++++++++++++++++++-
3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 5426627..dbc5e02 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -61,6 +61,8 @@
* interrupt handler after suspending interrupts. For system
* wakeup devices users need to implement wakeup detection in
* their interrupt handlers.
+ * IRQF_DELIVER_AS_NMI - Configure interrupt to be delivered as non-maskable, if
+ * supported by the chip.
*/
#define IRQF_SHARED 0x00000080
#define IRQF_PROBE_SHARED 0x00000100
@@ -74,6 +76,7 @@
#define IRQF_NO_THREAD 0x00010000
#define IRQF_EARLY_RESUME 0x00020000
#define IRQF_COND_SUSPEND 0x00040000
+#define IRQF_DELIVER_AS_NMI 0x00080000

#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 7271a2c..d2520ae 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -515,6 +515,8 @@ struct irq_chip {
* IRQCHIP_SKIP_SET_WAKE: Skip chip.irq_set_wake(), for this irq chip
* IRQCHIP_ONESHOT_SAFE: One shot does not require mask/unmask
* IRQCHIP_EOI_THREADED: Chip requires eoi() on unmask in threaded mode
+ * IRQCHIP_CAN_DELIVER_AS_NMI Chip can deliver interrupts it receives as non-
+ * maskable.
*/
enum {
IRQCHIP_SET_TYPE_MASKED = (1 << 0),
@@ -524,6 +526,7 @@ enum {
IRQCHIP_SKIP_SET_WAKE = (1 << 4),
IRQCHIP_ONESHOT_SAFE = (1 << 5),
IRQCHIP_EOI_THREADED = (1 << 6),
+ IRQCHIP_CAN_DELIVER_AS_NMI = (1 << 7),
};

#include <linux/irqdesc.h>
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index e3336d9..d058aa8 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1137,7 +1137,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
{
struct irqaction *old, **old_ptr;
unsigned long flags, thread_mask = 0;
- int ret, nested, shared = 0;
+ int ret, nested, shared = 0, deliver_as_nmi = 0;

if (!desc)
return -EINVAL;
@@ -1156,6 +1156,16 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
if (!(new->flags & IRQF_TRIGGER_MASK))
new->flags |= irqd_get_trigger_type(&desc->irq_data);

+ /* Only deliver as non-maskable interrupt if supported by chip. */
+ if (new->flags & IRQF_DELIVER_AS_NMI) {
+ if (desc->irq_data.chip->flags & IRQCHIP_CAN_DELIVER_AS_NMI) {
+ irqd_set_deliver_as_nmi(&desc->irq_data);
+ deliver_as_nmi = 1;
+ } else {
+ return -EINVAL;
+ }
+ }
+
/*
* Check whether the interrupt nests into another interrupt
* thread.
@@ -1166,6 +1176,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
ret = -EINVAL;
goto out_mput;
}
+
+ /* Don't allow nesting if interrupt will be delivered as NMI. */
+ if (deliver_as_nmi) {
+ ret = -EINVAL;
+ goto out_mput;
+ }
+
/*
* Replace the primary handler which was provided from
* the driver for non nested interrupt handling by the
@@ -1186,6 +1203,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
* thread.
*/
if (new->thread_fn && !nested) {
+ if (deliver_as_nmi)
+ goto out_mput;
+
ret = setup_irq_thread(new, irq, false);
if (ret)
goto out_mput;
--
2.7.4
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