cloud-hypervisor balloonMem adds virtio-mem and balloon

[vdbe]

Could not get balloonMem working on cloud-hypervisor and looked into it a bit and microvm.nix sets up the balloon device and hotplug_method=virtio-mem for cloud-hypervisor, I think this is not purpose.

# command from current/bin/microvm-run
cloud-hypervisor \
  --cpus 'boot=1' \
  --watchdog \
  --console null \
  --serial tty \
  --kernel /nix/store/4fa3ggf753cj5jkxmbi3cj34xyxrw72j-linux-6.6.51-dev/vmlinux \
  --initramfs /nix/store/rjnqw4y3nzs6dqrqsdv3nss5yaw9ankq-initrd-linux-6.6.51/initrd \
  --cmdline 'earlyprintk=ttyS0 console=ttyS0 reboot=t panic=-1 root=fstab loglevel=4 init=/nix/store/3vrxcx9lvsdfmpiv1bm3d747n1824840-nixos-system-plz-24.11pre-git/init regInfo=/nix/store/qg5lap6j4mld4l6yimdszxhnjd0958zl-closure-info/registration' \
  --seccomp true \
  --memory 'hotplug_method=virtio-mem,hotplug_size=2048M,hotplugged_size=2048M,mergeable=on,shared=off,size=4096M' \
  --balloon 'deflate_on_oom=on,free_page_reporting=on,size=2048M' \
  --disk 'path=/nix/store/mc13yzp4g4gajssyij1gd51mks2bsl7a-microvm-store-disk.erofs,readonly=on' \
  --api-socket plz.sock

got hotplug_method=virtio-mem working with

cloud-hypervisor \
  --kernel ~user/linux-cloud-hypervisor/arch/x86/boot/compressed/vmlinux.bin \
  --serial tty \
  --disk path=~user/focal-server-cloudimg-amd64.raw path=/tmp/ubuntu-cloudinit.img \
  --cmdline "console=hvc0 root=/dev/vda1 rw" \
  --cpus boot=4 \
  --memory size=1024M,hotplug_method=virtio-mem,hotplug_size=4G,hotplugged_size=4G \
  --net "tap=,mac=,ip=,mask=" \

microvm config of host

  microvm.vms.plz = {
    autostart = false;
    pkgs = null;
    config = {
      imports = [
        (
          { pkgs, ... }:
          {

            users.users.root.password = "toor123";
            microvm = {
              hypervisor = "cloud-hypervisor";
              balloonMem = 2048;
            };
            environment.systemPackages = with pkgs; [
              htop
            ];
            services.qemuGuest.enable = true;
          }
        )
      ];

    };
  };

following instruction from https://www.cloudhypervisor.org/docs/prologue/quick-start/ and https://www.cloudhypervisor.org/docs/prologue/quick-start/ but couldn't get it working for the nix vm.

The virtio memory get added to the vm I think but is not available, think something is missing on the guest.

Command

cloud-hypervisor \
  --cpus 'boot=1' \
  --watchdog \
  --console null \
  --serial tty \
  --kernel /nix/store/4fa3ggf753cj5jkxmbi3cj34xyxrw72j-linux-6.6.51-dev/vmlinux \
  --initramfs /nix/store/rjnqw4y3nzs6dqrqsdv3nss5yaw9ankq-initrd-linux-6.6.51/initrd \
  --cmdline 'earlyprintk=ttyS0 console=ttyS0 reboot=t panic=-1 root=fstab loglevel=4 init=/nix/store/3vrxcx9lvsdfmpiv1bm3d747n1824840-nixos-system-plz-24.11pre-git/init regInfo=/nix/store/qg5lap6j4mld4l6yimdszxhnjd0958zl-closure-info/registration' \
  --seccomp true --memory 'hotplug_method=virtio-mem,hotplug_size=2048M,hotplugged_size=2048M,mergeable=on,shared=off,size=4096M' \
  --disk 'path=/nix/store/mc13yzp4g4gajssyij1gd51mks2bsl7a-microvm-store-disk.erofs,readonly=on' \
  --api-socket plz.sock

Command

cloud-hypervisor \
  --cpus 'boot=1' \
  --watchdog \
  --console null \
  --serial tty \
  --kernel /nix/store/4fa3ggf753cj5jkxmbi3cj34xyxrw72j-linux-6.6.51-dev/vmlinux \
  --initramfs /nix/store/rjnqw4y3nzs6dqrqsdv3nss5yaw9ankq-initrd-linux-6.6.51/initrd \
  --cmdline 'earlyprintk=ttyS0 console=ttyS0 reboot=t panic=-1 root=fstab loglevel=4 init=/nix/store/3vrxcx9lvsdfmpiv1bm3d747n1824840-nixos-system-plz-24.11pre-git/init regInfo=/nix/store/qg5lap6j4mld4l6yimdszxhnjd0958zl-closure-info/registration' \
  --seccomp true --memory 'size=4096M' \
  --disk 'path=/nix/store/mc13yzp4g4gajssyij1gd51mks2bsl7a-microvm-store-disk.erofs,readonly=on' \
  --api-socket plz.sock