doc/virtio: add Virtio Block doc

I decided to use 'Virtio Block' as the title. Virtio spec uses the same name alongside SCSI. ``` 5 Device Types [...] 5.2 Block Device 5.6 SCSI Host Device ``` Also added a CHANGELOG note. Change-Id: Ie2eabd053213da776c78a8d938a621b42e6d5558 Signed-off-by: Dariusz Stojaczyk <[email protected]> Reviewed-on: https://review.gerrithub.io/408829 Reviewed-by: Daniel Verkamp <[email protected]> Tested-by: SPDK Automated Test System <[email protected]> Reviewed-by: John Kariuki <[email protected]> Reviewed-by: Pawel Wodkowski <[email protected]> Reviewed-by: Maciej Szwed <[email protected]> Reviewed-by: Jim Harris <[email protected]>
YMhuan · Apr 25, 2018 · 30f369f · 30f369f
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -106,6 +106,14 @@ The persistent memory (PMDK) bdev module is now enabled using --with-pmdk instea
 --with-nvml.  This reflects the renaming of the persistent memory library from NVML to
 PMDK.
 
+### Virtio Block driver
+
+A userspace driver for Virtio Block devices has been added. It was built on top of the
+[Virtio](http://www.spdk.io/doc/virtio.html) library and can be managed similarly to
+the Virtio SCSI driver. See the
+[Virtio Block](http://www.spdk.io/doc/bdev.html#bdev_config_virtio_blk) reference for
+more information.
+
 ## v18.01: Blobstore Thin Provisioning
 
 ### Build System

diff --git a/doc/bdev.md b/doc/bdev.md
@@ -304,3 +304,16 @@ Virtio-SCSI devices can be removed with the following command
 `rpc.py remove_virtio_scsi_bdev VirtioScsi0`
 
 Removing a Virtio-SCSI device will destroy all its bdevs.
+
+# Virtio Block {#bdev_config_virtio_blk}
+
+The Virtio-Block driver can expose an SPDK bdev from a Virtio-Block device.
+
+Virtio-Block bdevs are constructed the same way as Virtio-SCSI ones.
+
+`rpc.py construct_virtio_user_blk_bdev /tmp/virtio.0 VirtioBlk0 --vq-count 2 --vq-size 512`
+
+`rpc.py construct_virtio_pci_blk_bdev 0000:01:00.0 VirtioBlk1`
+
+Since they export only a single bdev, the Virtio-Block driver doesn't offer additional
+remove/destruct RPC calls. @ref bdev_ug_delete_bdev should be used instead.
diff --git a/doc/virtio.md b/doc/virtio.md
@@ -16,5 +16,5 @@ and context switching overhead of QEMU and guest kernel, significantly boosting
 the overall I/O performance.
 
 This Virtio library is currently used to implement two bdev modules:
-@ref bdev_config_virtio_scsi and Virtio Blk. These modules will export generic
-SPDK block devices usable by any SPDK application.
+@ref bdev_config_virtio_scsi and @ref bdev_config_virtio_blk.
+These modules will export generic SPDK block devices usable by any SPDK application.