config: fc: Don't expose disable_block_device_use

Relying on virtio-block is the *only* way to use Firecracker with Kata
Containers, as shared FS (virtio-{fs,fs-nydus,9p}) is not supported by
Firecracker.

As configuration doesn't make sense to be exposed, we hardcode the
`false` value in the Firecracker configuration structure.

Fixes: #3813

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

src/runtime/config/configuration-fc.toml.in

@@ -103,14 +103,6 @@ default_memory = @DEFMEMSZ@
 # Default 0
 #memory_offset = 0
 
-# Disable block device from being used for a container's rootfs.
-# In case of a storage driver like devicemapper where a container's
-# root file system is backed by a block device, the block device is passed
-# directly to the hypervisor for performance reasons.
-# This flag prevents the block device from being passed to the hypervisor,
-# 9pfs is used instead to pass the rootfs.
-disable_block_device_use = @DEFDISABLEBLOCK@
-
 # Block storage driver to be used for the hypervisor in case the container
 # rootfs is backed by a block device. This is virtio-scsi, virtio-blk
 # or nvdimm.

src/runtime/pkg/katautils/config.go

@@ -568,7 +568,7 @@ func newFirecrackerHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		EntropySource:         h.GetEntropySource(),
 		EntropySourceList:     h.EntropySourceList,
 		DefaultBridges:        h.defaultBridges(),
-		DisableBlockDeviceUse: h.DisableBlockDeviceUse,
+		DisableBlockDeviceUse: false, // shared fs is not supported in Firecracker,
 		HugePages:             h.HugePages,
 		Debug:                 h.Debug,
 		DisableNestingChecks:  h.DisableNestingChecks,