Qemu share folder - 9pnet_virtio: no channels available for device

Question

I try to run a qemu virtual machine having a folder shared with host. No matter what I do, I have always the same error: 9pnet_virtio: no channels available for device share.

Host machine is under Linux.

Kernel was compiled with all 9P and virtio options enabled (https://wiki.qemu.org/Documentation/9psetup).

Here's my script to run qemu:

#! /bin/bash

HDA=archlinux.img
HDB=myHome.img
KERNEL=linux/arch/x86/boot/bzImage

if [ -n "${KDB}" ]; then
    KGD_WAIT='kgdbwait'
fi

CMDLINE="root=/dev/sda1 rw vga=792 console=ttyS0 kgdboc=ttyS1 ${KGD_WAIT}"

FLAGS="--enable-kvm -s"
VIRTFS+=" --virtfs local,path=./share/,mount_tag=share,security_model=passthrough,id=share "

exec qemu-system-x86_64 ${FLAGS} \
     -hda "${HDA}" -hdb "${HDB}" \
     ${VIRTFS} \
     -net user -net nic \
     -serial stdio -serial tcp::1234,server,nowait \
     -boot c -m 1G \
     -kernel "${KERNEL}" -append "${CMDLINE}"

When I mount the folder manually (https://www.linux-kvm.org/page/9p_virtio)

mkdir share_folder
mount -t 9p -o trans=virtio,version=9p2000.L share share_folder

The result is the same.

Answer 1

Resolved for me (with an ubuntu 18.04 host and 14.04 guest) by adding theses modules:

• virtio_input
• 9pnet
• 9pnet_virtio

into guest file /etc/initramfs-tools/modules.

Don't forget to upadate initramfs for your kernel(s) after add:

update-initramfs -uk <kernel|all>

Answer 2

In my case it was failing due to missing virtio_pci module and I fixed it with:

modprobe virtio_pci