[PATCH V2 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

[Zhu Lingshan]

This patch introduce a set of functions for setup/unsetup
and update irq offloading respectively by register/unregister
and re-register the irq_bypass_producer.

Signed-off-by: Zhu Lingshan <lingshan....@intel.com>
Suggested-by: Jason Wang <jasow...@redhat.com>
---
 drivers/vhost/Kconfig |  1 +
 drivers/vhost/vdpa.c  | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index d3688c6..587fbae 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -65,6 +65,7 @@ config VHOST_VDPA
        tristate "Vhost driver for vDPA-based backend"
        depends on EVENTFD
        select VHOST
+       select IRQ_BYPASS_MANAGER
        depends on VDPA
        help
          This kernel module can be loaded in host kernel to accelerate
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 2fcc422..b9078d4 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -115,6 +115,43 @@ static irqreturn_t vhost_vdpa_config_cb(void *private)
        return IRQ_HANDLED;
 }
 
+static void vhost_vdpa_setup_vq_irq(struct vdpa_device *dev, int qid, int irq)
+{
+       struct vhost_vdpa *v = vdpa_get_drvdata(dev);
+       struct vhost_virtqueue *vq = &v->vqs[qid];
+       int ret;
+
+       spin_lock(&vq->call_ctx.ctx_lock);
+       if (!vq->call_ctx.ctx) {
+               spin_unlock(&vq->call_ctx.ctx_lock);
+               return;
+       }
+
+       vq->call_ctx.producer.token = vq->call_ctx.ctx;
+       vq->call_ctx.producer.irq = irq;
+       ret = irq_bypass_register_producer(&vq->call_ctx.producer);
+       spin_unlock(&vq->call_ctx.ctx_lock);
+}
+
+static void vhost_vdpa_unsetup_vq_irq(struct vdpa_device *dev, int qid)
+{
+       struct vhost_vdpa *v = vdpa_get_drvdata(dev);
+       struct vhost_virtqueue *vq = &v->vqs[qid];
+
+       spin_lock(&vq->call_ctx.ctx_lock);
+       irq_bypass_unregister_producer(&vq->call_ctx.producer);
+       spin_unlock(&vq->call_ctx.ctx_lock);
+}
+
+static void vhost_vdpa_update_vq_irq(struct vhost_virtqueue *vq)
+{
+       spin_lock(&vq->call_ctx.ctx_lock);
+       irq_bypass_unregister_producer(&vq->call_ctx.producer);
+       vq->call_ctx.producer.token = vq->call_ctx.ctx;
+       irq_bypass_register_producer(&vq->call_ctx.producer);
+       spin_unlock(&vq->call_ctx.ctx_lock);
+}
+
 static void vhost_vdpa_reset(struct vhost_vdpa *v)
 {
        struct vdpa_device *vdpa = v->vdpa;
@@ -332,6 +369,7 @@ static long vhost_vdpa_set_config_call(struct vhost_vdpa 
*v, u32 __user *argp)
 
        return 0;
 }
+
 static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
                                   void __user *argp)
 {
@@ -390,6 +428,14 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, 
unsigned int cmd,
                        cb.private = NULL;
                }
                ops->set_vq_cb(vdpa, idx, &cb);
+               /*
+                * if it has a non-zero irq, means there is a
+                * previsouly registered irq_bypass_producer,
+                * we should update it when ctx (its token)
+                * changes.
+                */
+               if (vq->call_ctx.producer.irq)
+                       vhost_vdpa_update_vq_irq(vq);
                break;
 
        case VHOST_SET_VRING_NUM:
@@ -951,6 +997,8 @@ static void vhost_vdpa_remove(struct vdpa_device *vdpa)
        },
        .probe  = vhost_vdpa_probe,
        .remove = vhost_vdpa_remove,
+       .setup_vq_irq = vhost_vdpa_setup_vq_irq,
+       .unsetup_vq_irq = vhost_vdpa_unsetup_vq_irq,
 };
 
 static int __init vhost_vdpa_init(void)
-- 
1.8.3.1