State of contrib/vhost-user-input?

["Alex Bennée" <alex.bennee@linaro.org>]

Hi,

I'm trying to get the contrib/vhost-user-input working but it exits
during the boot up sequence:

  ➜  gdb --args ./vhost-user-input -p /dev/input/event22 -s /tmp/mouse.sock
  GNU gdb (GDB) 15.0.50.20231012-git
  <snip>
  Reading symbols from ./vhost-user-input...
  (gdb) b map_ring
  Breakpoint 1 at 0x7634c: file ../../subprojects/libvhost-user/libvhost-user.c, line 618.
  (gdb) r
  Starting program: /home/alex/lsrc/qemu.git/builds/arm.debug/contrib/vhost-user-input/vhost-user-input -p /dev/input/event22 -s /tmp/mouse.sock
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  [New Thread 0x7ffff7afb6c0 (LWP 3807698)]
  ================ Vhost user message ================
  Request: VHOST_USER_GET_FEATURES (1)
  Flags:   0x1
  Size:    0
  Sending back to guest u64: 0x0000000175000000
  ================ Vhost user message ================
  Request: VHOST_USER_GET_PROTOCOL_FEATURES (15)
  Flags:   0x1
  Size:    0
  ================ Vhost user message ================
  Request: VHOST_USER_SET_PROTOCOL_FEATURES (16)
  Flags:   0x1
  Size:    8
  u64: 0x0000000000008e2b
  ================ Vhost user message ================
  Request: VHOST_USER_GET_QUEUE_NUM (17)
  Flags:   0x1
  Size:    0
  ================ Vhost user message ================
  Request: VHOST_USER_GET_MAX_MEM_SLOTS (36)
  Flags:   0x1
  Size:    0
  u64: 0x0000000000000020
  ================ Vhost user message ================
  Request: VHOST_USER_SET_BACKEND_REQ_FD (21)
  Flags:   0x9
  Size:    0
  Fds: 6
  Got backend_fd: 6
  ================ Vhost user message ================
  Request: VHOST_USER_SET_OWNER (3)
  Flags:   0x1
  Size:    0
  ================ Vhost user message ================
  Request: VHOST_USER_GET_FEATURES (1)
  Flags:   0x1
  Size:    0
  Sending back to guest u64: 0x0000000175000000
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_CALL (13)
  Flags:   0x1
  Size:    8
  Fds: 7
  u64: 0x0000000000000000
  Got call_fd: 7 for vq: 0
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_ERR (14)
  Flags:   0x1
  Size:    8
  Fds: 8
  u64: 0x0000000000000000
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_CALL (13)
  Flags:   0x1
  Size:    8
  Fds: 9
  u64: 0x0000000000000001
  Got call_fd: 9 for vq: 1
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_ERR (14)
  Flags:   0x1
  Size:    8
  Fds: 10
  u64: 0x0000000000000001
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_GET_CONFIG (24)
  Flags:   0x1
  Size:    148
  ================ Vhost user message ================
  Request: VHOST_USER_SET_FEATURES (2)
  Flags:   0x1
  Size:    8
  u64: 0x0000000170000000
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_NUM (8)
  Flags:   0x1
  Size:    8
  State.index: 0
  State.num:   64
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_BASE (10)
  Flags:   0x1
  Size:    8
  State.index: 0
  State.num:   0
  ================ Vhost user message ================
  Request: VHOST_USER_SET_VRING_ADDR (9)
  Flags:   0x1
  Size:    40
  vhost_vring_addr:
      index:  0
      flags:  0
      desc_user_addr:   0x00007f283491a000
      used_user_addr:   0x00007f283491a4c0
      avail_user_addr:  0x00007f283491a400
      log_guest_addr:   0x0000000100b1a4c0

  Thread 1 "vhost-user-inpu" hit Breakpoint 1, map_ring (dev=0x7fffffffdd60, vq=0x555555609ea0) at ../../subprojects/libvhost-user/libvhost-user.c:618
  warning: Source file is more recent than executable.
  618         vq->vring.desc = qva_to_va(dev, vq->vra.desc_user_addr);
  (gdb) s
  qva_to_va (dev=0x7fffffffdd60, qemu_addr=139810657378304) at ../../subprojects/libvhost-user/libvhost-user.c:231
  231         for (i = 0; i < dev->nregions; i++) {
  (gdb) p dev->nregions
  $1 = 0
  (gdb) n
  240         return NULL;
  (gdb)
  241     }
  (gdb) c
  Continuing.
  Setting virtq addresses:
      vring_desc  at (nil)
      vring_used  at (nil)
      vring_avail at (nil)

  ** (vhost-user-input:3807669): CRITICAL **: 17:16:14.554: Invalid vring_addr message

  [Thread 0x7ffff7afb6c0 (LWP 3807698) exited]
  [Inferior 1 (process 3807669) exited with code 01]
  (gdb) q

Which looks like libvhost-user is expecting
VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS to be negotiated and the
resulting VHOST_USER_ADD_MEM_REG to be sent. How is this meant to work
if the protocol feature isn't negotiated?

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro