Why AlmaLinux 10, Rocky Linux 10, and CentOS 10 Kernel Panic on KVM: Understanding the x86_64-v2 CPU Requirement

The launch of AlmaLinux 10, Rocky Linux 10, and CentOS Stream 10 has brought a wave of unexpected problems for VPS providers and home-lab users. One of the most common and frustrating issues is this:

The VM immediately kernel panics during boot.
Installers crash, consoles freeze, and some systems throw errors like:

• “kernel requires x86_64-v2”
• “illegal instruction”
• “general protection fault”
• “kernel panic — not syncing”

This is not a bug in the operating system.
It’s caused by a major architectural change: RHEL 10 and its rebuilds now require a newer CPU baseline—x86_64-v2.

Below is a clear explanation of why this breaks KVM virtualization and how to fix it.

The Move to x86_64-v2: What Changed?

For nearly two decades, Linux distributions used the original x86_64 instruction set introduced in the mid-2000s. That’s no longer the case.

Starting with RHEL 10 and all rebuilds (AlmaLinux 10, Rocky 10, CentOS 10), the compiler baseline has been raised to:

x86_64-v2 Minimum CPU Feature Level

This includes essential CPU instructions such as:

• SSE3
• SSSE3
• SSE4.1 & SSE4.2
• CMPXCHG16B
• POPCNT
• LZCNT
• MOVBE

Modern physical CPUs support these, but virtualization complicates things.
A KVM virtual machine only sees the CPU features the hypervisor exposes — and many platforms expose an outdated or stripped-down virtual CPU.

When these instructions are missing, the OS cannot run, resulting in immediate kernel panic.

Why KVM Machines Are Affected Most

KVM allows you to assign CPU “models” to a VM. Many virtualization systems still default to models like:

• qemu64
• kvm64
• athlon
• core2duo

These CPU models do not meet the x86_64-v2 requirement, even if your host CPU itself is new and fully compatible.

This issue appears on:

• Proxmox (older nodes or default CPU type)
• libvirt / raw QEMU setups
• Virtualizor
• SolusVM
• VirtFusion
• OpenStack clusters
• LXD/Incus KVM VMs using old machine types

Booting AlmaLinux 10 or Rocky 10 with one of these old CPU profiles results in:

• failure to launch the kernel
• early systemd crashes
• the installer halting instantly
• “unsupported CPU level” messages

Why the Kernel Panics Occur

When the OS boots, the kernel checks your CPU feature set.
If any required instruction from the x86_64-v2 baseline is missing, the kernel stops immediately.

It’s not optional.
The entire OS is compiled assuming these features exist.

This affects:

• bootloaders
• early userspace
• systemd
• cryptographic routines
• GCC-compiled binaries
• glibc and core libraries

One missing instruction = instant crash.

How to Fix This (The Correct Way for KVM Users & Hosts)

Enable CPU Passthrough (Best Solution)

This exposes the host’s actual CPU to the VM.