Re: State of contrib/vhost-user-input?

[Marc-André Lureau]

Hi Alex

On Mon, Oct 23, 2023 at 8:34 PM Alex Bennée <alex.bennee@linaro.org> wrote:
>
>
> 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?


How did you start QEMU ? Did you forget to use shared memory ? We
should probably add some error at QEMU level when vhost-user devices
are used without shared memory!