[Qemu-devel] [PATCH 9/9] virtio-blk: add num-queues device property

[Stefan Hajnoczi <stefanha@redhat.com>]

Multiqueue virtio-blk can be enabled as follows:

  qemu -device virtio-blk-pci,num-queues=8

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/virtio-blk.c          | 15 +++++++++++++--
 include/hw/virtio/virtio-blk.h |  1 -
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 64b4185..383e060 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -740,6 +740,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     blkcfg.physical_block_exp = get_physical_block_exp(conf);
     blkcfg.alignment_offset = 0;
     blkcfg.wce = blk_enable_write_cache(s->blk);
+    virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues);
     memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
 }
 
@@ -783,6 +784,9 @@ static uint64_t virtio_blk_get_features(VirtIODevice *vdev, uint64_t features,
     if (blk_is_read_only(s->blk)) {
         virtio_add_feature(&features, VIRTIO_BLK_F_RO);
     }
+    if (s->conf.num_queues > 1) {
+        virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
+    }
 
     return features;
 }
@@ -1008,6 +1012,7 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
     VirtIOBlkConf *conf = &s->conf;
     Error *err = NULL;
     static int virtio_blk_id;
+    unsigned i;
 
     if (!conf->conf.blk) {
         error_setg(errp, "drive property not set");
@@ -1017,6 +1022,10 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
         error_setg(errp, "Device needs media, but drive is empty");
         return;
     }
+    if (!conf->num_queues) {
+        error_setg(errp, "num-queues property must be larger than 0");
+        return;
+    }
 
     blkconf_serial(&conf->conf, &conf->serial);
     s->original_wce = blk_enable_write_cache(conf->conf.blk);
@@ -1034,8 +1043,9 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
     s->rq = NULL;
     s->sector_mask = (s->conf.conf.logical_block_size / BDRV_SECTOR_SIZE) - 1;
 
-    conf->num_queues = 1;
-    s->vq = virtio_add_queue(vdev, 128, virtio_blk_handle_output);
+    for (i = 0; i < conf->num_queues; i++) {
+        virtio_add_queue(vdev, 128, virtio_blk_handle_output);
+    }
     virtio_blk_data_plane_create(vdev, conf, &s->dataplane, &err);
     if (err != NULL) {
         error_propagate(errp, err);
@@ -1094,6 +1104,7 @@ static Property virtio_blk_properties[] = {
 #endif
     DEFINE_PROP_BIT("request-merging", VirtIOBlock, conf.request_merging, 0,
                     true),
+    DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 0bf9ebc..06148ea 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -47,7 +47,6 @@ struct VirtIOBlockReq;
 typedef struct VirtIOBlock {
     VirtIODevice parent_obj;
     BlockBackend *blk;
-    VirtQueue *vq;
     void *rq;
 
     /* The following two fields are used only during save/load */
-- 
2.5.5