vhost_vdpa: remove unnecessary spin_lock in vhost_vring_call

This commit removed unnecessary spin_locks in vhost_vring_call
and related operations. Because we manipulate irq offloading
contents in vhost_vdpa ioctl code path which is already
protected by dev mutex and vq mutex.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Link: https://lore.kernel.org/r/20200909065234.3313-1-lingshan.zhu@intel.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vhost/vdpa.c

@@ -96,26 +96,20 @@ static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
 		return;
 
 	irq = ops->get_vq_irq(vdpa, qid);
-	spin_lock(&vq->call_ctx.ctx_lock);
 	irq_bypass_unregister_producer(&vq->call_ctx.producer);
-	if (!vq->call_ctx.ctx || irq < 0) {
-		spin_unlock(&vq->call_ctx.ctx_lock);
+	if (!vq->call_ctx.ctx || irq < 0)
 		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 vhost_vdpa *v, u16 qid)
 {
 	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_reset(struct vhost_vdpa *v)

drivers/vhost/vhost.c

@@ -302,7 +302,6 @@ static void vhost_vring_call_reset(struct vhost_vring_call *call_ctx)
 {
 	call_ctx->ctx = NULL;
 	memset(&call_ctx->producer, 0x0, sizeof(struct irq_bypass_producer));
-	spin_lock_init(&call_ctx->ctx_lock);
 }
 
 static void vhost_vq_reset(struct vhost_dev *dev,
@@ -1650,9 +1649,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			break;
 		}
 
-		spin_lock(&vq->call_ctx.ctx_lock);
 		swap(ctx, vq->call_ctx.ctx);
-		spin_unlock(&vq->call_ctx.ctx_lock);
 		break;
 	case VHOST_SET_VRING_ERR:
 		if (copy_from_user(&f, argp, sizeof f)) {

drivers/vhost/vhost.h

@@ -64,7 +64,6 @@ enum vhost_uaddr_type {
 struct vhost_vring_call {
 	struct eventfd_ctx *ctx;
 	struct irq_bypass_producer producer;
-	spinlock_t ctx_lock;
 };
 
 /* The virtqueue structure describes a queue attached to a device. */