configure: introduce --enable-vhost-user-blk-server

Make it possible to compile out the vhost-user-blk server. It is enabled
by default on Linux.

Note that vhost-user-server.c depends on libvhost-user, which requires
CONFIG_LINUX. The CONFIG_VHOST_USER dependency was erroneous since that
option controls vhost-user frontends (previously known as "master") and
not device backends (previously known as "slave").

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201027173528.213464-3-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

block/export/export.c

@@ -22,13 +22,13 @@
 #include "qapi/qapi-commands-block-export.h"
 #include "qapi/qapi-events-block-export.h"
 #include "qemu/id.h"
-#if defined(CONFIG_LINUX) && defined(CONFIG_VHOST_USER)
+#ifdef CONFIG_VHOST_USER_BLK_SERVER
 #include "vhost-user-blk-server.h"
 #endif
 
 static const BlockExportDriver *blk_exp_drivers[] = {
     &blk_exp_nbd,
-#if defined(CONFIG_LINUX) && defined(CONFIG_VHOST_USER)
+#ifdef CONFIG_VHOST_USER_BLK_SERVER
     &blk_exp_vhost_user_blk,
 #endif
 };

block/export/meson.build

@@ -1,2 +1,2 @@
 blockdev_ss.add(files('export.c'))
-blockdev_ss.add(when: ['CONFIG_LINUX', 'CONFIG_VHOST_USER'], if_true: files('vhost-user-blk-server.c'))
+blockdev_ss.add(when: 'CONFIG_VHOST_USER_BLK_SERVER', if_true: files('vhost-user-blk-server.c'))

configure

@@ -329,6 +329,7 @@ vhost_crypto=""
 vhost_scsi=""
 vhost_vsock=""
 vhost_user=""
+vhost_user_blk_server=""
 vhost_user_fs=""
 kvm="auto"
 hax="auto"
@@ -1246,6 +1247,10 @@ for opt do
   ;;
   --enable-vhost-vsock) vhost_vsock="yes"
   ;;
+  --disable-vhost-user-blk-server) vhost_user_blk_server="no"
+  ;;
+  --enable-vhost-user-blk-server) vhost_user_blk_server="yes"
+  ;;
   --disable-vhost-user-fs) vhost_user_fs="no"
   ;;
   --enable-vhost-user-fs) vhost_user_fs="yes"
@@ -1791,6 +1796,7 @@ disabled with --disable-FEATURE, default is enabled if available:
   vhost-crypto    vhost-user-crypto backend support
   vhost-kernel    vhost kernel backend support
   vhost-user      vhost-user backend support
+  vhost-user-blk-server    vhost-user-blk server support
   vhost-vdpa      vhost-vdpa kernel backend support
   spice           spice
   rbd             rados block device (rbd)
@@ -2382,6 +2388,12 @@ if test "$vhost_net" = ""; then
   test "$vhost_kernel" = "yes" && vhost_net=yes
 fi
 
+# libvhost-user is Linux-only
+test "$vhost_user_blk_server" = "" && vhost_user_blk_server=$linux
+if test "$vhost_user_blk_server" = "yes" && test "$linux" = "no"; then
+  error_exit "--enable-vhost-user-blk-server is only available on Linux"
+fi
+
 ##########################################
 # pkg-config probe
 
@@ -6275,6 +6287,9 @@ fi
 if test "$vhost_vdpa" = "yes" ; then
   echo "CONFIG_VHOST_VDPA=y" >> $config_host_mak
 fi
+if test "$vhost_user_blk_server" = "yes" ; then
+  echo "CONFIG_VHOST_USER_BLK_SERVER=y" >> $config_host_mak
+fi
 if test "$vhost_user_fs" = "yes" ; then
   echo "CONFIG_VHOST_USER_FS=y" >> $config_host_mak
 fi

util/meson.build

@@ -66,7 +66,7 @@ if have_block
   util_ss.add(files('main-loop.c'))
   util_ss.add(files('nvdimm-utils.c'))
   util_ss.add(files('qemu-coroutine.c', 'qemu-coroutine-lock.c', 'qemu-coroutine-io.c'))
-  util_ss.add(when: ['CONFIG_LINUX', 'CONFIG_VHOST_USER'], if_true: [
+  util_ss.add(when: 'CONFIG_LINUX', if_true: [
     files('vhost-user-server.c'), vhost_user
   ])
   util_ss.add(files('block-helpers.c'))