vhost-user-blk: introduce a new vhost-user-blk host device

This commit introduces a new vhost-user device for block, it uses a
chardev to connect with the backend, same with Qemu virito-blk device,
Guest OS still uses the virtio-blk frontend driver.

To use it, start QEMU with command line like this:

qemu-system-x86_64 \
    -chardev socket,id=char0,path=/path/vhost.socket \
    -device vhost-user-blk-pci,chardev=char0,num-queues=2, \
            bootindex=2... \

Users can use different parameters for `num-queues` and `bootindex`.

Different with exist Qemu virtio-blk host device, it makes more easy
for users to implement their own I/O processing logic, such as all
user space I/O stack against hardware block device. It uses the new
vhost messages(VHOST_USER_GET_CONFIG) to get block virtio config
information from backend process.

Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/default-configs/s390x-softmmu.mak b/default-configs/s390x-softmmu.mak
index 444bf16b80..2f4bfe73b4 100644
--- a/default-configs/s390x-softmmu.mak
+++ b/default-configs/s390x-softmmu.mak
@@ -1,6 +1,7 @@
 CONFIG_PCI=y
 CONFIG_VIRTIO_PCI=$(CONFIG_PCI)
 CONFIG_VHOST_USER_SCSI=$(call land,$(CONFIG_VHOST_USER),$(CONFIG_LINUX))
+CONFIG_VHOST_USER_BLK=$(call land,$(CONFIG_VHOST_USER),$(CONFIG_LINUX))
 CONFIG_VIRTIO=y
 CONFIG_SCLPCONSOLE=y
 CONFIG_TERMINAL3270=y