id = 1337
title = "Incorrect warnings when using vhost without numa"
state = "opened"
created_at = "2022-11-23T18:14:05.536Z"
closed_at = "n/a"
labels = ["Documentation", "device:virtio"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/1337"
host-os = "Ubuntu 22.04"
host-arch = "x86_64"
qemu-version = "QEMU emulator version 7.1.92 (v7.1.0-1922-g7c09a7f6ae)"
guest-os = "Linux - built with vsock support (`CONFIG_VSOCKETS`)"
guest-arch = "mips or x86_64"
description = """Part A: Misleading error message. Running the above command for any architecture fails to initialize vhost, and prints the following, incorrect advice
```
qemu-system-mips: Failed initializing vhost-user memory map, consider using -object memory-backend-file share=on
qemu-system-mips: vhost_set_mem_table failed: Invalid argument (22)
qemu-system-mips: Error starting vhost: 22
```

Since the command line already contains `-object memory-backend-file,id=mem1,mem-path=/tmp/mem,size=256M,share=on` this error message should not be printed. For x86_64, this can be resolved by adding `-numa node,memdev=mem0` to the command line. As such, I think this error message should instead guide a user to adding that argument.

Part B: No documented configuration to run vhost-user for machines that don't support numa.
The mips malta machine does not support the `-numa` flag. It is unclear if this means that `vhost` cannot be used with this platform or if a non-numa configuration with a memory-backend-file can be used."""
reproduce = """1. Run `vhost-user-vsock --socket=/tmp/vhost4.socket --uds-path=/tmp/foo` from https://github.com/rust-vmm/vhost-device.
1. Run the above QEMU command"""
additional = "n/a"