Looks like my others (Digital Ocean, Vultr) use KVM (according to virt-what).
Did anyone see Amazon do reboots? I wonder if Amazon has some method of hot-patching kernel and Xen code under the hood? There are such things, and that would be some interesting secret sauce.
> Our team has been working around-the-clock to find ways to minimize the impact for those requiring a reboot. We're happy to share that we'll now be able to live-update the vast majority of our older hardware for this Xen Security Advisory.
https://aws.amazon.com/premiumsupport/maintenance-2015-03/
There's been a few subsequent articles mentioning Amazon's ability to hot-patch Xen without a reboot. They didn't perform a reboot for this vulnerability.
Luckily, many people also converted to HVM over PV already. IIRC it was largely PV instances in EC2 classic... but I can't be sure.
Regardless of the virtualization technology, you need to keep on top of disclosures. Any public provider running xen should be on the disclosure list by now http://www.xenproject.org/security-policy.html