Yesterday I wanted to install Slackware64-current in a KVM host. I grabbed the iso (thanks to alienbob) and I started the installation process.
When it was time to install lilo I chose expert and I changed the disk from sda to vda and I also added: bios = 0x80 max-partitions = 7.
Despite the above settings lilo was complaining with: "linux experimental device 0xfd00 needs to be defined"

I ended up to change the disk driver from virtio to ide but I would like to know what I was missing or doing wrong...

I guess the virtio driver is mising or not loaded anyway. I am running several Slackware VM's on a Proxmox VE server,and always use the IDE driver. Works fine.

I checked for virtio in the config-huge and it seems most of the virtio modules are already built-in:

grep 'VIRTIO' config-huge-5.4.44.x64
CONFIG_BLK_MQ_VIRTIO=y
CONFIG_VIRTIO_VSOCKETS=m
CONFIG_VIRTIO_VSOCKETS_COMMON=m
CONFIG_NET_9P_VIRTIO=y
CONFIG_VIRTIO_BLK=y
# CONFIG_VIRTIO_BLK_SCSI is not set
CONFIG_SCSI_VIRTIO=y
CONFIG_VIRTIO_NET=y
CONFIG_VIRTIO_CONSOLE=y
CONFIG_HW_RANDOM_VIRTIO=y
CONFIG_DRM_VIRTIO_GPU=m
CONFIG_VIRTIO=y
CONFIG_VIRTIO_MENU=y
CONFIG_VIRTIO_PCI=y
CONFIG_VIRTIO_PCI_LEGACY=y
CONFIG_VIRTIO_PMEM=m
CONFIG_VIRTIO_BALLOON=y
CONFIG_VIRTIO_INPUT=m
CONFIG_VIRTIO_MMIO=y
# CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES is not set
CONFIG_RPMSG_VIRTIO=m
CONFIG_VIRTIO_FS=m
CONFIG_CRYPTO_DEV_VIRTIO=m

I found a similar problem: https://www.linuxquestions.org/quest...-issue-871981/ that goes back to 2011 and the suggestion was to use a generic kernel with a initrd. But it seems that nowadays the huge kernel has the necessary modules like CONFIG_VIRTIO_BLK already built-in.

I run a variety of Slackware guests for testing, clean compiles/packages and various other nonsense. I've noted that on the 14.2 and current guests, using huge.s, the built in virtio modules aren't detected/used/loaded for some reason. I never did figure out why. maybe some qemu/KVM quirk? I thus always use generic kernel + initrd. A side effect is that the generic kernel has a smaller memory footprint - handy back when my host was RAM limited.