10 files changed, 45 insertions, 24 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index e2ed69f1c430..ee175ff17256 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9432,7 +9432,6 @@ F:	include/media/videobuf2-*
 
 VIRTIO CONSOLE DRIVER
 M:      Amit Shah <amit.shah@redhat.com>
-L:      virtio-dev@lists.oasis-open.org
 L:      virtualization@lists.linux-foundation.org
 S:      Maintained
 F:      drivers/char/virtio_console.c
@@ -9442,7 +9441,6 @@ F:	include/uapi/linux/virtio_console.h
 VIRTIO CORE, NET AND BLOCK DRIVERS
 M:      Rusty Russell <rusty@rustcorp.com.au>
 M:      "Michael S. Tsirkin" <mst@redhat.com>
-L:      virtio-dev@lists.oasis-open.org
 L:      virtualization@lists.linux-foundation.org
 S:      Maintained
 F:      drivers/virtio/
@@ -9455,7 +9453,6 @@ F:	include/uapi/linux/virtio_*.h
 VIRTIO HOST (VHOST)
 M:      "Michael S. Tsirkin" <mst@redhat.com>
 L:      kvm@vger.kernel.org
-L:      virtio-dev@lists.oasis-open.org
 L:      virtualization@lists.linux-foundation.org
 L:      netdev@vger.kernel.org
 S:      Maintained
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 0eace43cea11..6d8a87f252de 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -158,6 +158,7 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
         unsigned long flags;
         unsigned int num;
         const bool last = (req->cmd_flags & REQ_END) != 0;
+        int err;
 
         BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
 
@@ -198,11 +199,16 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
         }
 
         spin_lock_irqsave(&vblk->vq_lock, flags);
-        if (__virtblk_add_req(vblk->vq, vbr, vbr->sg, num) < 0) {
+        err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num);
+        if (err) {
                 virtqueue_kick(vblk->vq);
                 spin_unlock_irqrestore(&vblk->vq_lock, flags);
                 blk_mq_stop_hw_queue(hctx);
-                return BLK_MQ_RQ_QUEUE_BUSY;
+                /* Out of mem doesn't actually happen, since we fall back
+                 * to direct descriptors */
+                if (err == -ENOMEM || err == -ENOSPC)
+                        return BLK_MQ_RQ_QUEUE_BUSY;
+                return BLK_MQ_RQ_QUEUE_ERROR;
         }
 
         if (last)
@@ -485,10 +491,11 @@ static struct blk_mq_ops virtio_mq_ops = {
 static struct blk_mq_reg virtio_mq_reg = {
         .ops            = &virtio_mq_ops,
         .nr_hw_queues   = 1,
-        .queue_depth    = 64,
+        .queue_depth    = 0, /* Set in virtblk_probe */
         .numa_node      = NUMA_NO_NODE,
         .flags          = BLK_MQ_F_SHOULD_MERGE,
 };
+module_param_named(queue_depth, virtio_mq_reg.queue_depth, uint, 0444);
 
 static int virtblk_init_vbr(void *data, struct blk_mq_hw_ctx *hctx,
                              struct request *rq, unsigned int nr)
@@ -553,6 +560,13 @@ static int virtblk_probe(struct virtio_device *vdev)
                 goto out_free_vq;
         }
 
+        /* Default queue sizing is to fill the ring. */
+        if (!virtio_mq_reg.queue_depth) {
+                virtio_mq_reg.queue_depth = vblk->vq->num_free;
+                /* ... but without indirect descs, we use 2 descs per req */
+                if (!virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC))
+                        virtio_mq_reg.queue_depth /= 2;
+        }
         virtio_mq_reg.cmd_size =
                 sizeof(struct virtblk_req) +
                 sizeof(struct scatterlist) * sg_elems;
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index c12398d1517c..2ce0e225e58c 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -47,8 +47,7 @@ static void register_buffer(u8 *buf, size_t size)
         sg_init_one(&sg, buf, size);
 
         /* There should always be room for one buffer. */
-        if (virtqueue_add_inbuf(vq, &sg, 1, buf, GFP_KERNEL) < 0)
-                BUG();
+        virtqueue_add_inbuf(vq, &sg, 1, buf, GFP_KERNEL);
 
         virtqueue_kick(vq);
 }
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 841b60831df1..470b01f3e7b4 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -938,7 +938,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
         sgs[out_num] = &stat;
 
         BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
-        BUG_ON(virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC) < 0);
+        virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);
 
         if (unlikely(!virtqueue_kick(vi->cvq)))
                 return status == VIRTIO_NET_OK;
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 34bdabaecbd6..25ebe8eecdb7 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -108,8 +108,7 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 
         /* We should always be able to add one buffer to an empty queue. */
-        if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0)
-                BUG();
+        virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
         virtqueue_kick(vq);
 
         /* When host has read buffer, this completes via balloon_ack */
@@ -258,8 +257,7 @@ static void stats_handle_request(struct virtio_balloon *vb)
         if (!virtqueue_get_buf(vq, &len))
                 return;
         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
-        if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0)
-                BUG();
+        virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
         virtqueue_kick(vq);
 }
 
@@ -310,6 +308,12 @@ static int balloon(void *_vballoon)
                 else if (diff < 0)
                         leak_balloon(vb, -diff);
                 update_balloon_size(vb);
+
+                /*
+                 * For large balloon changes, we could spend a lot of time
+                 * and always have work to do.  Be nice if preempt disabled.
+                 */
+                cond_resched();
         }
         return 0;
 }
@@ -338,7 +342,7 @@ static int init_vqs(struct virtio_balloon *vb)
 
                 /*
                  * Prime this virtqueue with one buffer so the hypervisor can
-                 * use it to signal us later.
+                 * use it to signal us later (it can't be broken yet!).
                  */
                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)