Please keep this document in mind when using these guest kernel configuration files.
Firecracker as a virtual machine monitor is designed and built for use with specific goals, so these kernel configurations are tuned to be secure and to use the host's resources as optimally as possible, specifically allowing for as many guests to be running concurrently as possible (high density).
For example, one of the mechanisms to improve density is to reduce virtual memory areas of the guest. This decreases the page table size and improves available memory on the host for other guests to occupy. As Firecracker is intended for ephemeral compute (short-lived environments, not intended to run indefinitely), a Firecracker guest is not expected to require large memory sizes.
One interesting use-case where this can be seen to cause odd side affects is one where golang's race detector for aarch64 expected a 48-bit space, but the guest's kernel config enforced 39-bit. See Firecracker issue #3514.