When a VPS provider mentions VT-x or AMD-V, it is not talking about a brand but about a specific set of processor instructions, without which modern virtualization would run an order of magnitude slower. This article is for anyone who wants to understand exactly what a hypervisor checks before starting a virtual machine, and why some images refuse to start at all without this feature.
What hardware processor virtualization is
VT-x is a set of instruction-set extensions for Intel processors that make it easier for a hypervisor to manage the memory and interrupts of virtual machines. AMD-V solves the same problem for AMD processors. Before these extensions existed, a hypervisor had to emulate privileged instructions in software, intercepting and rewriting the guest operating system's code on the fly — that is called software virtualization, and it runs noticeably slower.
With hardware support, the processor itself can switch between host mode and guest mode without calling the hypervisor for every privileged operation. Because of this, the speed difference between a guest system and the physical hardware becomes barely noticeable for most workloads.
How to check whether hardware virtualization is enabled
On a Linux server, one command is enough to see whether the processor supports the needed extension:
egrep -c '(vmx|svm)' /proc/cpuinfoThe vmx flag means VT-x support on Intel processors, the svm flag means AMD-V support on AMD processors. If the command returns zero, support is either physically absent, disabled in the BIOS or UEFI, or unavailable inside a top-level virtual machine — nested virtualization requires a separate switch on the hypervisor, covered in detail in the article "How to create a virtual machine in Proxmox".
VT-x and AMD-V: the difference for a user
For an ordinary administrator of a virtual server, the difference between the two technologies is barely noticeable — both solve the same task on different processor architectures. The difference shows up only at the level of the virtualization platform and its related set of technologies.
| Parameter | VT-x (Intel) | AMD-V (AMD) |
|---|---|---|
| Flag in /proc/cpuinfo | vmx | svm |
| Memory extension | EPT (Extended Page Tables) | RVI / NPT (Nested Page Tables) |
| Processor vendor | Intel | AMD |
| Nested virtualization support | Available, once enabled on the hypervisor | Available, once enabled on the hypervisor |
Platforms such as Proxmox VE use both extensions in a way that stays equally transparent to the user — a description of the platform itself is in the article "Proxmox: what it is".
Why hardware virtualization matters to a VPS tenant
For a customer who rents a ready-made virtual machine, hardware virtualization works invisibly — the provider has already enabled it at the hypervisor level. It is worth knowing about in a few specific cases:
- Running a nested virtual machine inside a rented VPS, for testing or a hypervisor of one's own
- Using Docker and other container technologies, which partly rely on the same kernel extensions
- Diagnosing a performance drop, when software emulation needs to be ruled out as a cause
After such a check it helps to move straight on to deploying a working virtual machine — the steps are described in the article "Virtualization on a dedicated server".
What to do if hardware virtualization is unavailable
If the check showed that the needed flag is missing, it helps to go through the steps in the following order.
- Confirm that the physical server's processor supports VT-x or AMD-V at all, according to the manufacturer's documentation
- Enter the BIOS or UEFI settings and find the entry responsible for processor virtualization — it may be named differently by different board manufacturers
- Enable the relevant entry and save the settings with a server restart
- Repeat the vmx or svm flag check after the system boots
- If the server is rented from a provider, contact support and ask them to enable nested virtualization at the hypervisor level
Frequently asked questions
Does a virtual machine work at all without VT-x or AMD-V?
Modern hypervisors are mostly built around hardware virtualization and either refuse to start a guest system without it or fall back to software emulation with a noticeable speed loss. Relying on that fallback mode in a production environment is not a good idea.
Can VT-x be enabled programmatically, without entering the BIOS?
No, this is a setting of the processor itself at the board firmware level, and the operating system cannot change it from software. The only way is to enter the BIOS or UEFI while the server boots.
Does VT-x affect the performance of ordinary programs without virtualization?
No, with the extension enabled but no virtual machines running, the processor's behavior for ordinary applications does not change — the instruction set stays available but sits idle.