I feel vindicated :). We put in a lot of effort with great customers to get nested virtualization running well on GCE years ago, and I'm glad to hear AWS is coming around.

You can tell people to just do something else, there's probably a separate natural solution, etc. but sometimes you're willing to sacrifice some peak performance just have that uniformity of operations and control.

This is a big deal because you can now run Firecracker/other microVMs in an AWS VM instead of expensive AWS bare-metal instances.

GCP has had nested virtualization for a while.

• iJohnDoe

  today at 1:27 AM

  Was hoping this comment would be here. Firecracker and microVMs are good use-case. Also, being able to simply test and develop is a nice to have.

  Nested virtualization can mean a lot of things. Not just full VMs.

• parhamn

  today at 1:15 AM

  whats the ~ perf hit of something like this?

  • otterley

    today at 1:40 AM

    As a practical matter, anywhere from 5-15%.

  • largbae

    today at 1:25 AM

    Nowadays nested just wastes the extra operating system overhead and I/O performance if your VM doesn't have paravirtualization drivers installed. CPUs all have hardware support.

> Nested virtualization is supported only on 8th generation Intel-based instance types (c8i, m8i, r8i, and their flex variants). When nested virtualization is enabled, Virtual Secure Mode (VSM) is automatically disabled for the instance.

I wonder if this is connected to Azure launching OpenShift Virtualization on "Boost" SKUs? There are a lot of VMWare customers going to OpenShift Virt, and apparently the CPU/memory overhead on Azure maxes out around 10% under full load... but then hyper V has been doing a lot of work on it. No idea if nitro includes any of the KVM-on-KVM passthrough of full KVM, to give it an edge here.

Support for nested virtualization has been added to the main SDKs. In the us-west-2 region, you can already see the "Nested Virtualization" option and use it with the new M8id, C8id, and R8id instance types.

This is really big news for micro-VM sandbox solutions like E2B, which I work on.

I wonder if this will extend SEV-SNP and TDX to the child VMs?

I wonder if providers like Hetzner and Digital Ocean etc. will get this someday also.

welcome AWS to 2018!

• ssl-3

  today at 1:08 AM

  Yep. It's pretty boring. I've been using it at home for years and years with libvirt on very not-special consumer hardware. I guess the AWS clown is finally catching up on this one little not-new-at-all thing.

  • otterley

    today at 1:38 AM

    I was an Amazon EC2 Specialist SA in a prior role, so I know a little about this.

    If EC2 were like your home server, you might be right. And an EC2 bare metal instance is the closest approximation to that. On bare metal, you've always been free to run your own VMs, and we had some customers who rolled their own nested VM implementations on it.

    But EC2 is not like your home server. There are some nontrivial considerations and requirements to offer nested virtualization at cloud scale:

    1. Ensuring virtualized networking (VPC) works with nested VMs as well as with the primary VM

    2. Making sure the environment (VMM etc) is sufficiently hardened to meet AWS's incredibly stringent security standards so that nesting doesn't pose unintended threats or weaken EC2's isolation properties. EC2 doesn't use libvirt or an off-the-shelf KVM. See https://youtu.be/cD1mNQ9YbeA?si=hcaZaV2W_hcEIn9L&t=1095 and https://youtu.be/hqqKi3E-oG8?si=liAfollyupYicc_L&t=501

    3. Ensuring performance and reliability meets customer standards

    4. Building a rock-solid control plane around it all

    It's not a trivial matter of flipping a bit.

    • QuinnyPig

      today at 2:12 AM

      I always enjoy the color you add to these conversations. Thanks!

    • raw_anon_1111

      today at 2:20 AM

      Seriously curious, don’t Firecracker VMs already run on EC2 instances under the hood when they host Lambda and Fargate?

      • otterley

        today at 2:24 AM

        Unfortunately I'm not at liberty to dive deep into those details. I will say that Firecracker can be used on bare metal EC2 instances, whether you're a public customer or AWS itself. :-)

        • raw_anon_1111

          today at 2:41 AM

          I guess I should have peeked at the source code when I was there…

      • wmf

        today at 2:36 AM

        Since I don't work for AWS I'm allowed to say that at the scale of millions/billions of microVMs you're better off running them on bare metal instances to avoid the overhead of nested virtualization.

    • sitole

      today at 2:15 AM

      Nitro is very interesting stuff

Could someone explain why this is might be a big deal?

I remember playing with nested virty some years ago and deciding it is a backwards step except for PoC and the like. Given I haven't personally run out of virty gear, I never needed to do a PoC.

• paulfurtado

  today at 1:19 AM

  It is great for isolation. There are so many VM based containerization solutions at this point, like Kata Containers, gvisor, and Firecracker. With kata, your kubernetes pods run in isolated VMs. It also opens the door for live migration of apps between ec2 instances, making some kinds of maintenance easier when you have persistent workloads. Even if not for security, there are so many ways a workload can break a machine such that you need to reboot or replace (like detaching an ebs volume with a mounted xfs filesystem at the wrong moment).

  The place I've probably wanted it the most though is in CI/CD systems: it's always been annoying to build and test system images in EC2 in a generic way.

  It also allows for running other third party appliances unmodified in EC2.

  But also, almost every other execution environment offers this: GCP, VMWare, KVM, etc, so it's frustrating that EC2 has only offered it on their bare metal instance types. When ec2 was using xen 10+ years ago, it made sense, but they've been on kvm since the inception of nitro.

• today at 1:43 AM

• UltraSane

  today at 1:20 AM

  You can now run VMs inside a cheaper AWS instance instead of having to pay for an entire bare-metal instance. This is useful for things like network simulation where you use QEMU to emulate network hardware.

Would love to see performance numbers with nested virtualization, particularly that of IO-bound workloads.

Would these thing be good for openclaw, agents?

• CuriouslyC

  today at 2:03 AM

  Yeah, though honestly if I'm deploying anything I'd just build an image with nix rather than use nested virtualization.

What's the performance impact for nested virtualization in general? I'd think this would be adding multiple layers of MMU overhead.

• blibble

  today at 2:08 AM

  depends on the workload and how they've done it

  pure CPU should be essentially unaffected, if they're not emulating the MMU/page tables in software

  the difference in IO ranges from barely measurable to absolutely horrible, depending on their implementation

  traps/vmexits have another layer to pass through (and back)

• dwattttt

  today at 1:16 AM

  From memory, the virtualisation operations themselves aren't nested. The VM instructions interact with the external virtualisation hardware, so it's more of a cooperative situation, e.g. a guest can create & manage virtualisation structures that are run alongside it.

  I don't know if this applies to the specific nested virtualisation AWS are providing though.

• otterley

  today at 2:00 AM

  As a practical matter, anywhere from 5-15%.

• gchamonlive

  today at 12:53 AM

  Highly doubt that

Sounds expensive for legacy apps

hell yes, finally

"* *Feature*: Launching nested virtualization. This feature allows you to run nested VMs inside virtual (non-bare metal) EC2 instances."