LoongArch: Add irq_work support via self IPIs

Add irq_work support for LoongArch via self IPIs. This make it possible
to run works in hardware interrupt context, which is a prerequisite for
NOHZ_FULL.

Implement:
 - arch_irq_work_raise()
 - arch_irq_work_has_interrupt()
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/hardirq.h

@@ -12,11 +12,12 @@
 extern void ack_bad_irq(unsigned int irq);
 #define ack_bad_irq ack_bad_irq
 
-#define NR_IPI	2
+#define NR_IPI	3
 
 enum ipi_msg_type {
 	IPI_RESCHEDULE,
 	IPI_CALL_FUNCTION,
+	IPI_IRQ_WORK,
 };
 
 typedef struct {

arch/loongarch/include/asm/irq_work.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_LOONGARCH_IRQ_WORK_H
+#define _ASM_LOONGARCH_IRQ_WORK_H
+
+static inline bool arch_irq_work_has_interrupt(void)
+{
+	return IS_ENABLED(CONFIG_SMP);
+}
+
+#endif /* _ASM_LOONGARCH_IRQ_WORK_H */

arch/loongarch/include/asm/smp.h

@@ -69,9 +69,11 @@ extern int __cpu_logical_map[NR_CPUS];
 #define ACTION_BOOT_CPU	0
 #define ACTION_RESCHEDULE	1
 #define ACTION_CALL_FUNCTION	2
+#define ACTION_IRQ_WORK		3
 #define SMP_BOOT_CPU		BIT(ACTION_BOOT_CPU)
 #define SMP_RESCHEDULE		BIT(ACTION_RESCHEDULE)
 #define SMP_CALL_FUNCTION	BIT(ACTION_CALL_FUNCTION)
+#define SMP_IRQ_WORK		BIT(ACTION_IRQ_WORK)
 
 struct secondary_data {
 	unsigned long stack;

arch/loongarch/kernel/paravirt.c

@@ -2,6 +2,7 @@
 #include <linux/export.h>
 #include <linux/types.h>
 #include <linux/interrupt.h>
+#include <linux/irq_work.h>
 #include <linux/jump_label.h>
 #include <linux/kvm_para.h>
 #include <linux/static_call.h>
@@ -97,6 +98,11 @@ static irqreturn_t pv_ipi_interrupt(int irq, void *dev)
 		info->ipi_irqs[IPI_CALL_FUNCTION]++;
 	}
 
+	if (action & SMP_IRQ_WORK) {
+		irq_work_run();
+		info->ipi_irqs[IPI_IRQ_WORK]++;
+	}
+
 	return IRQ_HANDLED;
 }
 

arch/loongarch/kernel/smp.c

@@ -13,6 +13,7 @@
 #include <linux/cpumask.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
+#include <linux/irq_work.h>
 #include <linux/profile.h>
 #include <linux/seq_file.h>
 #include <linux/smp.h>
@@ -70,6 +71,7 @@ static DEFINE_PER_CPU(int, cpu_state);
 static const char *ipi_types[NR_IPI] __tracepoint_string = {
 	[IPI_RESCHEDULE] = "Rescheduling interrupts",
 	[IPI_CALL_FUNCTION] = "Function call interrupts",
+	[IPI_IRQ_WORK] = "IRQ work interrupts",
 };
 
 void show_ipi_list(struct seq_file *p, int prec)
@@ -217,6 +219,13 @@ void arch_smp_send_reschedule(int cpu)
 }
 EXPORT_SYMBOL_GPL(arch_smp_send_reschedule);
 
+#ifdef CONFIG_IRQ_WORK
+void arch_irq_work_raise(void)
+{
+	mp_ops.send_ipi_single(smp_processor_id(), ACTION_IRQ_WORK);
+}
+#endif
+
 static irqreturn_t loongson_ipi_interrupt(int irq, void *dev)
 {
 	unsigned int action;
@@ -234,6 +243,11 @@ static irqreturn_t loongson_ipi_interrupt(int irq, void *dev)
 		per_cpu(irq_stat, cpu).ipi_irqs[IPI_CALL_FUNCTION]++;
 	}
 
+	if (action & SMP_IRQ_WORK) {
+		irq_work_run();
+		per_cpu(irq_stat, cpu).ipi_irqs[IPI_IRQ_WORK]++;
+	}
+
 	return IRQ_HANDLED;
 }