What is SVM mode in BIOS and what does it do?

Question

I was poking around in my PC's BIOS settings and noticed an option called "SVM Mode". It was disabled by default on my system.

I'm curious what SVM mode actually does and in what situations it should be enabled vs disabled. From some quick searching, it seems SVM has to do with AMD CPUs and virtualization. But I'd like to understand more specifically:

What does the SVM acronym stand for?
How does enabling SVM mode change how the CPU and system operate?
Are there any performance impacts or security considerations to enabling SVM?
In what use cases would you want to turn on SVM mode?

If anyone can shed some light on this BIOS setting and provide a simple explanation of its purpose and effects, I'd appreciate it! I'm running an AMD Ryzen CPU if that matters.

Maisie Azalea · Accepted Answer

SVM stands for Secure Virtual Machine. It is AMD's hardware virtualization technology, equivalent to Intel's VT-x. SVM provides hardware extensions that allow virtual machines (VMs) to have direct access to the CPU, which improves virtualization performance and security.

How SVM changes CPU and system operation:

With SVM enabled, the CPU can operate in two modes: root mode (for the host OS) and non-root mode (for guest VMs).
SVM introduces new instructions and memory management features that facilitate efficient virtualization.
It allows VMs to execute privileged instructions directly on the CPU without hypervisor intervention in most cases, reducing virtualization overhead.

Performance and security considerations:

Enabling SVM can improve performance of virtualization workloads by reducing the overhead of virtualizing hardware.
It enhances security by providing better isolation between the host OS and guest VMs. Features like AMD-V with IOMMU can prevent unauthorized memory access.
For non-virtualization workloads, enabling SVM has minimal impact on performance and security.

Use cases for enabling SVM:

If you run virtual machines using hypervisors like VMware, VirtualBox, Hyper-V, or KVM, enabling SVM will generally provide better performance.
SVM is required for running 64-bit guest operating systems, even if the host OS is 32-bit.
Enabling SVM is necessary for using hardware passthrough to give VMs direct access to physical devices.
Some security features like Windows Credential Guard and Device Guard require SVM to be enabled.

In summary, SVM is AMD's hardware virtualization technology that allows virtual machines to execute more directly on the CPU, improving performance and security. It's primarily beneficial if you use virtualization software, but has minimal impact otherwise. On AMD Ryzen systems, enabling SVM in the BIOS is recommended if you plan to run virtual machines.