The x86_64 kernel has minor support for KVM Qemu. These options are already enabled
CONFIG_VIRTIO_BLK=m
CONFIG_VIRTIO_NET=m
CONFIG_VIRTIO_PCI=m
But there is a lot VIRTIO devices not enabled
CONFIG_BLK_MQ_VIRTIO=y
CONFIG_VIRTIO_VSOCKETS=m
CONFIG_VIRTIO_VSOCKETS_COMMON=m
CONFIG_BT_VIRTIO=m
CONFIG_NET_9P_VIRTIO=m
CONFIG_SCSI_VIRTIO=m
CONFIG_VIRTIO_CONSOLE=m
CONFIG_HW_RANDOM_VIRTIO=m
CONFIG_I2C_VIRTIO=m
CONFIG_GPIO_VIRTIO=m
CONFIG_DRM_VIRTIO_GPU=m
CONFIG_DRM_VIRTIO_GPU_KMS=y
CONFIG_SND_VIRTIO=m
CONFIG_VIRTIO_ANCHOR=y
CONFIG_VIRTIO=y
CONFIG_VIRTIO_PCI_LIB=m
CONFIG_VIRTIO_PCI_LIB_LEGACY=m
CONFIG_VIRTIO_MENU=y
CONFIG_VIRTIO_PCI_LEGACY=y
CONFIG_VIRTIO_VDPA=m
CONFIG_VIRTIO_PMEM=m
CONFIG_VIRTIO_BALLOON=m
CONFIG_VIRTIO_MEM=m
CONFIG_VIRTIO_INPUT=m
CONFIG_VIRTIO_MMIO=m
CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=y
CONFIG_VIRTIO_DMA_SHARED_BUFFER=m
CONFIG_XEN_VIRTIO=y
CONFIG_XEN_VIRTIO_FORCE_GRANT is not set
CONFIG_VIRTIO_IOMMU=m
CONFIG_RPMSG_VIRTIO=m
CONFIG_VIRTIO_FS=m
CONFIG_CRYPTO_DEV_VIRTIO=m
There is no technical reason why this are not enabled. Can you please add this options to the amd64-volumio-min-*_defconfig ?
These will make the KVM support faster and smoother.