[RFC v4 10/11] vduse: Introduce a workqueue for irq injection

[Xie Yongji]

This patch introduces a workqueue to support injecting
virtqueue's interrupt asynchronously. This is mainly
for performance considerations which makes sure the push()
and pop() for used vring can be asynchronous.

Signed-off-by: Xie Yongji <xieyon...@bytedance.com>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c 
b/drivers/vdpa/vdpa_user/vduse_dev.c
index 8042d3fa57f1..f5adeb9ee027 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -42,6 +42,7 @@ struct vduse_virtqueue {
        spinlock_t irq_lock;
        struct eventfd_ctx *kickfd;
        struct vdpa_callback cb;
+       struct work_struct inject;
 };
 
 struct vduse_dev;
@@ -99,6 +100,7 @@ static DEFINE_IDA(vduse_ida);
 
 static dev_t vduse_major;
 static struct class *vduse_class;
+static struct workqueue_struct *vduse_irq_wq;
 
 static inline struct vduse_dev *vdpa_to_vduse(struct vdpa_device *vdpa)
 {
@@ -852,6 +854,17 @@ static int vduse_kickfd_setup(struct vduse_dev *dev,
        return 0;
 }
 
+static void vduse_vq_irq_inject(struct work_struct *work)
+{
+       struct vduse_virtqueue *vq = container_of(work,
+                                       struct vduse_virtqueue, inject);
+
+       spin_lock_irq(&vq->irq_lock);
+       if (vq->ready && vq->cb.callback)
+               vq->cb.callback(vq->cb.private);
+       spin_unlock_irq(&vq->irq_lock);
+}
+
 static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg)
 {
@@ -917,12 +930,7 @@ static long vduse_dev_ioctl(struct file *file, unsigned 
int cmd,
                        break;
 
                vq = &dev->vqs[arg];
-               spin_lock_irq(&vq->irq_lock);
-               if (vq->ready && vq->cb.callback) {
-                       vq->cb.callback(vq->cb.private);
-                       ret = 0;
-               }
-               spin_unlock_irq(&vq->irq_lock);
+               queue_work(vduse_irq_wq, &vq->inject);
                break;
        }
        case VDUSE_INJECT_CONFIG_IRQ:
@@ -1109,6 +1117,7 @@ static int vduse_create_dev(struct vduse_dev_config 
*config)
 
        for (i = 0; i < dev->vq_num; i++) {
                dev->vqs[i].index = i;
+               INIT_WORK(&dev->vqs[i].inject, vduse_vq_irq_inject);
                spin_lock_init(&dev->vqs[i].kick_lock);
                spin_lock_init(&dev->vqs[i].irq_lock);
        }
@@ -1333,6 +1342,11 @@ static int vduse_init(void)
        if (ret)
                goto err_chardev;
 
+       vduse_irq_wq = alloc_workqueue("vduse-irq",
+                               WQ_HIGHPRI | WQ_SYSFS | WQ_UNBOUND, 0);
+       if (!vduse_irq_wq)
+               goto err_wq;
+
        ret = vduse_domain_init();
        if (ret)
                goto err_domain;
@@ -1344,6 +1358,8 @@ static int vduse_init(void)
        return 0;
 err_mgmtdev:
        vduse_domain_exit();
+err_wq:
+       destroy_workqueue(vduse_irq_wq);
 err_domain:
        unregister_chrdev_region(vduse_major, VDUSE_DEV_MAX);
 err_chardev:
@@ -1359,6 +1375,7 @@ static void vduse_exit(void)
        misc_deregister(&vduse_misc);
        class_destroy(vduse_class);
        unregister_chrdev_region(vduse_major, VDUSE_DEV_MAX);
+       destroy_workqueue(vduse_irq_wq);
        vduse_domain_exit();
        vduse_mgmtdev_exit();
 }
-- 
2.11.0