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

[Alex Bennée]

Marc-André Lureau <marcandre.lureau@redhat.com> writes:

> 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 ?

I had:

       -m 8192 \
       -object memory-backend-memfd,id=mem,size=8G,share=on \

Alongside:

       -device virtio-gpu-pci \
       -device qemu-xhci -device usb-kbd \
       -kernel ~/lsrc/linux.git/builds/arm64/arch/arm64/boot/Image.gz -append 
'console=ttyAMA0 root=/dev/sda2' \
       -display gtk,gl=on \
       -chardev socket,id=mouse2,path=/tmp/mouse.sock -device 
vhost-user-input-pci,chardev=mouse2

I even double checked with the generic device I was working with:

       -chardev socket,id=mouse2,path=/tmp/mouse.sock -device 
vhost-user-device-pci,chardev=mouse2,virtio-id=18,config_size=136,num_vqs=2

> We should probably add some error at QEMU level when vhost-user devices
> are used without shared memory!

That would certainly be a good idea.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro