[Qemu-devel] [PATCH v2 5/8] virtio-blk: multiqueue batch notify

[Stefan Hajnoczi]

The batch notification BH needs to know which virtqueues to notify when
multiqueue is enabled.  Use a bitmap to track the virtqueues with
pending notifications.

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 hw/block/virtio-blk.c          | 29 +++++++++++++++++++++++++----
 include/hw/virtio/virtio-blk.h |  1 +
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index c8d66f0..9de749b 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -54,11 +54,28 @@ static void virtio_blk_batch_notify_bh(void *opaque)
 {
     VirtIOBlock *s = opaque;
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
+    unsigned nvqs = s->conf.num_queues;
+    unsigned long bitmap[BITS_TO_LONGS(nvqs)];
+    unsigned j;
 
-    if (s->dataplane_started && !s->dataplane_disabled) {
-        virtio_blk_data_plane_notify(s->dataplane, s->vq);
-    } else {
-        virtio_notify(vdev, s->vq);
+    memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
+    memset(s->batch_notify_vqs, 0, sizeof(bitmap));
+
+    for (j = 0; j < nvqs; j += BITS_PER_LONG) {
+        unsigned long bits = bitmap[j];
+
+        while (bits != 0) {
+            unsigned i = j + ctzl(bits);
+            VirtQueue *vq = virtio_get_queue(vdev, i);
+
+            if (s->dataplane_started && !s->dataplane_disabled) {
+                virtio_blk_data_plane_notify(s->dataplane, vq);
+            } else {
+                virtio_notify(vdev, vq);
+            }
+
+            bits &= bits - 1; /* clear right-most bit */
+        }
     }
 }
 
@@ -97,6 +114,8 @@ static void virtio_blk_req_complete(VirtIOBlockReq *req, 
unsigned char status)
 
     stb_p(&req->in->status, status);
     virtqueue_push(req->vq, &req->elem, req->in_len);
+
+    set_bit(virtio_queue_get_id(req->vq), s->batch_notify_vqs);
     qemu_bh_schedule(s->batch_notify_bh);
 }
 
@@ -940,6 +959,7 @@ static void virtio_blk_device_realize(DeviceState *dev, 
Error **errp)
         return;
     }
 
+    s->batch_notify_vqs = bitmap_new(conf->num_queues);
     blk_add_aio_context_notifier(s->blk, virtio_blk_attached_aio_context,
                                  virtio_blk_detach_aio_context, s);
     virtio_blk_attached_aio_context(blk_get_aio_context(s->blk), s);
@@ -961,6 +981,7 @@ static void virtio_blk_device_unrealize(DeviceState *dev, 
Error **errp)
     blk_remove_aio_context_notifier(s->blk, virtio_blk_attached_aio_context,
                                     virtio_blk_detach_aio_context, s);
     virtio_blk_detach_aio_context(s);
+    g_free(s->batch_notify_vqs);
     virtio_blk_data_plane_destroy(s->dataplane);
     s->dataplane = NULL;
     qemu_del_vm_change_state_handler(s->change);
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 487b28d..b6e7860 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -51,6 +51,7 @@ typedef struct VirtIOBlock {
     void *rq;
     QEMUBH *bh;
     QEMUBH *batch_notify_bh;
+    unsigned long *batch_notify_vqs;
     VirtIOBlkConf conf;
     unsigned short sector_mask;
     bool original_wce;
-- 
2.5.5