Describe the bug
A clear and concise description of what the bug is.

Without explicit huge pages, the VM memory is only aligned to 4 KiB. This means that the entire VM is likely to only get 4 KiB EPT entries, instead of 2 MiB or 1 GiB. This leads to reduced memory performance due to TLB pressure.

I have a PR to expose an option for alignment in vm-memory here: rust-vmm/vm-memory#375

To Reproduce
Steps to reproduce the behaviour:
Launch any VM with N GiB of memory, with or without THP. Observe that (unless you get lucky), /sys/kernel/debug/kvm/pages_2m is 0.

From looking at the code, I observed that QEMU and OpenVMM do align their memory.

Version

Output of cloud-hypervisor --version:
v51.1

Did you build from source, if so build command line (e.g. features):
No
VM configuration

What command line did you run (or JSON config data):
Launch a VM with a decent amount of memory (512 MiB, 1 GiB+), with THP but not explicit huge pages.

Guest OS version details:
https://github.com/cloud-hypervisor/linux

Host OS version details:
Observed on Azure Linux, Ubuntu 20, and Amazon Linux 3.

Logs
N/A, let me know if needed
Output of cloud-hypervisor -v from either standard error or via --log-file:

Linux kernel output:
Ditto