Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

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On 2020/7/31 下午2:55, Zhu Lingshan wrote:
This commit introduces struct vhost_vring_call which replaced
raw struct eventfd_ctx *call_ctx in struct vhost_virtqueue.
Besides eventfd_ctx, it contains a spin lock and an
irq_bypass_producer in its structure.

Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
Suggested-by: Jason Wang <jasowang@xxxxxxxxxx>
---
  drivers/vhost/vdpa.c  |  4 ++--
  drivers/vhost/vhost.c | 22 ++++++++++++++++------
  drivers/vhost/vhost.h |  9 ++++++++-
  3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index a54b60d6623f..df3cf386b0cd 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -96,7 +96,7 @@ static void handle_vq_kick(struct vhost_work *work)
  static irqreturn_t vhost_vdpa_virtqueue_cb(void *private)
  {
  	struct vhost_virtqueue *vq = private;
-	struct eventfd_ctx *call_ctx = vq->call_ctx;
+	struct eventfd_ctx *call_ctx = vq->call_ctx.ctx;
if (call_ctx)
  		eventfd_signal(call_ctx, 1);
@@ -382,7 +382,7 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
  		break;
case VHOST_SET_VRING_CALL:
-		if (vq->call_ctx) {
+		if (vq->call_ctx.ctx) {
  			cb.callback = vhost_vdpa_virtqueue_cb;
  			cb.private = vq;
  		} else {
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index d7b8df3edffc..9f1a845a9302 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -298,6 +298,13 @@ static void vhost_vq_meta_reset(struct vhost_dev *d)
  		__vhost_vq_meta_reset(d->vqs[i]);
  }
+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,
  			   struct vhost_virtqueue *vq)
  {
@@ -319,13 +326,13 @@ static void vhost_vq_reset(struct vhost_dev *dev,
  	vq->log_base = NULL;
  	vq->error_ctx = NULL;
  	vq->kick = NULL;
-	vq->call_ctx = NULL;
  	vq->log_ctx = NULL;
  	vhost_reset_is_le(vq);
  	vhost_disable_cross_endian(vq);
  	vq->busyloop_timeout = 0;
  	vq->umem = NULL;
  	vq->iotlb = NULL;
+	vhost_vring_call_reset(&vq->call_ctx);
  	__vhost_vq_meta_reset(vq);
  }
@@ -685,8 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
  			eventfd_ctx_put(dev->vqs[i]->error_ctx);
  		if (dev->vqs[i]->kick)
  			fput(dev->vqs[i]->kick);
-		if (dev->vqs[i]->call_ctx)
-			eventfd_ctx_put(dev->vqs[i]->call_ctx);
+		if (dev->vqs[i]->call_ctx.ctx)
+			eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
  		vhost_vq_reset(dev, dev->vqs[i]);
  	}
  	vhost_dev_free_iovecs(dev);
@@ -1629,7 +1636,10 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
  			r = PTR_ERR(ctx);
  			break;
  		}
-		swap(ctx, vq->call_ctx);
+
+		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)) {
@@ -2440,8 +2450,8 @@ static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  {
  	/* Signal the Guest tell them we used something up. */
-	if (vq->call_ctx && vhost_notify(dev, vq))
-		eventfd_signal(vq->call_ctx, 1);
+	if (vq->call_ctx.ctx && vhost_notify(dev, vq))
+		eventfd_signal(vq->call_ctx.ctx, 1);
  }
  EXPORT_SYMBOL_GPL(vhost_signal);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index c8e96a095d3b..38eb1aa3b68d 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -13,6 +13,7 @@
  #include <linux/virtio_ring.h>
  #include <linux/atomic.h>
  #include <linux/vhost_iotlb.h>
+#include <linux/irqbypass.h>
struct vhost_work;
  typedef void (*vhost_work_fn_t)(struct vhost_work *work);
@@ -60,6 +61,12 @@ enum vhost_uaddr_type {
  	VHOST_NUM_ADDRS = 3,
  };
+struct vhost_vring_call {
+	struct eventfd_ctx *ctx;
+	struct irq_bypass_producer producer;
+	spinlock_t ctx_lock;


It's not clear to me why we need ctx_lock here.

Thanks


+};
+
  /* The virtqueue structure describes a queue attached to a device. */
  struct vhost_virtqueue {
  	struct vhost_dev *dev;
@@ -72,7 +79,7 @@ struct vhost_virtqueue {
  	vring_used_t __user *used;
  	const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS];
  	struct file *kick;
-	struct eventfd_ctx *call_ctx;
+	struct vhost_vring_call call_ctx;
  	struct eventfd_ctx *error_ctx;
  	struct eventfd_ctx *log_ctx;




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