vhost: max s/g to match qemu

Qemu supports up to UIO_MAXIOV s/g so we have to match that because guest
drivers may rely on this.

Allocate indirect and log arrays dynamically to avoid using too much contigious
memory and make the length of hdr array to match the header length since each
iovec entry has a least one byte.

Test with copying large files w/ and w/o migration in both linux and windows
guests.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 48 insertions, 1 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index dd3d6f7406f8..344019774ddd 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -212,6 +212,45 @@ static int vhost_worker(void *data)
 	}
 }
 
+/* Helper to allocate iovec buffers for all vqs. */
+static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
+{
+	int i;
+	for (i = 0; i < dev->nvqs; ++i) {
+		dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
+					       UIO_MAXIOV, GFP_KERNEL);
+		dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
+					  GFP_KERNEL);
+		dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
+					    UIO_MAXIOV, GFP_KERNEL);
+
+		if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
+			!dev->vqs[i].heads)
+			goto err_nomem;
+	}
+	return 0;
+err_nomem:
+	for (; i >= 0; --i) {
+		kfree(dev->vqs[i].indirect);
+		kfree(dev->vqs[i].log);
+		kfree(dev->vqs[i].heads);
+	}
+	return -ENOMEM;
+}
+
+static void vhost_dev_free_iovecs(struct vhost_dev *dev)
+{
+	int i;
+	for (i = 0; i < dev->nvqs; ++i) {
+		kfree(dev->vqs[i].indirect);
+		dev->vqs[i].indirect = NULL;
+		kfree(dev->vqs[i].log);
+		dev->vqs[i].log = NULL;
+		kfree(dev->vqs[i].heads);
+		dev->vqs[i].heads = NULL;
+	}
+}
+
 long vhost_dev_init(struct vhost_dev *dev,
 		    struct vhost_virtqueue *vqs, int nvqs)
 {
@@ -229,6 +268,9 @@ long vhost_dev_init(struct vhost_dev *dev,
 	dev->worker = NULL;
 
 	for (i = 0; i < dev->nvqs; ++i) {
+		dev->vqs[i].log = NULL;
+		dev->vqs[i].indirect = NULL;
+		dev->vqs[i].heads = NULL;
 		dev->vqs[i].dev = dev;
 		mutex_init(&dev->vqs[i].mutex);
 		vhost_vq_reset(dev, dev->vqs + i);
@@ -295,6 +337,10 @@ static long vhost_dev_set_owner(struct vhost_dev *dev)
 	if (err)
 		goto err_cgroup;
 
+	err = vhost_dev_alloc_iovecs(dev);
+	if (err)
+		goto err_cgroup;
+
 	return 0;
 err_cgroup:
 	kthread_stop(worker);
@@ -345,6 +391,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 			fput(dev->vqs[i].call);
 		vhost_vq_reset(dev, dev->vqs + i);
 	}
+	vhost_dev_free_iovecs(dev);
 	if (dev->log_ctx)
 		eventfd_ctx_put(dev->log_ctx);
 	dev->log_ctx = NULL;
@@ -947,7 +994,7 @@ static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
 	}
 
 	ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
-			     ARRAY_SIZE(vq->indirect));
+			     UIO_MAXIOV);
 	if (unlikely(ret < 0)) {
 		vq_err(vq, "Translation failure %d in indirect.\n", ret);
 		return ret;