[PATCH v2 06/11] vduse: Support automatic irq callback affinity

[Xie Yongji]

This brings current interrupt affinity spreading mechanism
to vduse device. We will make use of irq_create_affinity_masks()
to create an irq callback affinity mask for each virtqueue of
vduse device. Then we will choose the CPU which has the lowest
number of interrupt allocated in the affinity mask to run the
irq callback.

Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 50 ++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index d126f3e32a20..90c2896039d9 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -23,6 +23,7 @@
 #include <linux/nospec.h>
 #include <linux/vmalloc.h>
 #include <linux/sched/mm.h>
+#include <linux/interrupt.h>
 #include <uapi/linux/vduse.h>
 #include <uapi/linux/vdpa.h>
 #include <uapi/linux/virtio_config.h>
@@ -58,6 +59,8 @@ struct vduse_virtqueue {
 	struct work_struct inject;
 	struct work_struct kick;
 	int irq_effective_cpu;
+	struct cpumask irq_affinity;
+	spinlock_t irq_affinity_lock;
 };
 
 struct vduse_dev;
@@ -123,6 +126,7 @@ struct vduse_control {
 
 static DEFINE_MUTEX(vduse_lock);
 static DEFINE_IDR(vduse_idr);
+static DEFINE_PER_CPU(unsigned long, vduse_allocated_irq);
 
 static dev_t vduse_major;
 static struct class *vduse_class;
@@ -710,6 +714,49 @@ static u32 vduse_vdpa_get_generation(struct vdpa_device *vdpa)
 	return dev->generation;
 }
 
+static void vduse_vq_update_effective_cpu(struct vduse_virtqueue *vq)
+{
+	unsigned int cpu, best_cpu;
+	unsigned long allocated, allocated_min = UINT_MAX;
+
+	spin_lock(&vq->irq_affinity_lock);
+
+	best_cpu = vq->irq_effective_cpu;
+	if (best_cpu != -1)
+		per_cpu(vduse_allocated_irq, best_cpu) -= 1;
+
+	for_each_cpu(cpu, &vq->irq_affinity) {
+		allocated = per_cpu(vduse_allocated_irq, cpu);
+		if (!cpu_online(cpu) || allocated >= allocated_min)
+			continue;
+
+		best_cpu = cpu;
+		allocated_min = allocated;
+	}
+	vq->irq_effective_cpu = best_cpu;
+	per_cpu(vduse_allocated_irq, best_cpu) += 1;
+
+	spin_unlock(&vq->irq_affinity_lock);
+}
+
+static void vduse_vdpa_set_irq_affinity(struct vdpa_device *vdpa,
+					struct irq_affinity *desc)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	struct irq_affinity_desc *affd = NULL;
+	int i;
+
+	affd = irq_create_affinity_masks(dev->vq_num, desc);
+	if (!affd)
+		return;
+
+	for (i = 0; i < dev->vq_num; i++) {
+		cpumask_copy(&dev->vqs[i]->irq_affinity, &affd[i].mask);
+		vduse_vq_update_effective_cpu(dev->vqs[i]);
+	}
+	kfree(affd);
+}
+
 static int vduse_vdpa_set_map(struct vdpa_device *vdpa,
 				unsigned int asid,
 				struct vhost_iotlb *iotlb)
@@ -760,6 +807,7 @@ static const struct vdpa_config_ops vduse_vdpa_config_ops = {
 	.get_config		= vduse_vdpa_get_config,
 	.set_config		= vduse_vdpa_set_config,
 	.get_generation		= vduse_vdpa_get_generation,
+	.set_irq_affinity	= vduse_vdpa_set_irq_affinity,
 	.reset			= vduse_vdpa_reset,
 	.set_map		= vduse_vdpa_set_map,
 	.free			= vduse_vdpa_free,
@@ -1380,6 +1428,8 @@ static int vduse_dev_init_vqs(struct vduse_dev *dev, u32 vq_align, u32 vq_num)
 		INIT_WORK(&dev->vqs[i]->kick, vduse_vq_kick_work);
 		spin_lock_init(&dev->vqs[i]->kick_lock);
 		spin_lock_init(&dev->vqs[i]->irq_lock);
+		spin_lock_init(&dev->vqs[i]->irq_affinity_lock);
+		cpumask_setall(&dev->vqs[i]->irq_affinity);
 	}
 
 	return 0;
-- 
2.20.1