Tutorial for passing through a Nvidia RTX graphics card to a Windows 10 virtual machine using a modified VBIOS
Recently I replaced my old NEC MultiSync 2690 HD screen for a HP DreamColor wide gamut screen with a 2560 x 1440 pixel resolution. The Nvidia GTX 970 GPU I used, though still perfectly capable at HD resolution, is likely to get challenged by higher resolutions. Moreover, the new Nvidia Studio driver doesn’t support models before the Geforce 1000 series, and I do want the 30 bpp (bit-per-pixel) support that this driver provides. Time for an upgrade – the Gigabyte RTX 2070 Super GPU.
VFIO is about running for example Windows 10 in a virtual machine (VM), using a discrete graphics card that you pass through to the VM. The Linux driver framework that is used to bind the graphics card during the host boot is called VFIO. The virtual machine itself (e.g. Windows 10) then uses its own native graphics driver to drive the GPU, significantly boosting VM graphics performance. This enables you to run Linux on the host and create Windows virtual machines for gaming and other high performance tasks.
AMD graphics cards have been plagued with the notorious FLR reset bug over several years now. Independent developers wrote a kernel patch as a workaround that would work most of the time. But the patch required kernel or module compilation, which is not everyone’s cup of tea.
Yesterday Wendell at Level1Techs posted a (p)review of the latest AMD Radeon 6800 and 6800XT graphics cards. He attests that the AMD Radeon 6800/6800XT are perfectly suitable for VFIO passthrough. No more FLR reset bug. Wendell goes further to point out that the Linux graphics drivers available in Ubuntu 20.04 already support these cards. This is great news for the Linux user community in general, and VFIO passthrough enthusiasts especially! Finally an alternative to NVIDIA.
There are more good news: Those of you who already own an AMD Navi, Vega or Polaris graphics card plagued with the FLR reset bug can now enjoy a simpler, better workaround. Instead of compiling the patch into the kernel, all you need to do now is to “build the module and modprobe it, or use dmks to manage it directly”.
AMD has already shown its Linux support through its open source graphics drivers. The new graphics cards based on the RDNA2 architecture have finally corrected the product flaw of previous releases. Welcome to the VFIO club.
You will probably have to wait some time to get hold of one of these cards, as they seem to have sold out on launch day.
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I’ve already written a detailed tutorial on Windows 10 kvm VGA passthrough based on QEMU version 2.11. Years have passed and recent distributions like Ubuntu 20.04, Linux Mint 20, or Manjaro come with QEMU 4.0, 4.2 or 5.1.
It wasn’t easy this time. Don’t get me wrong – the VFIO passthrough part, though challenging in some ways, went quite well. All in all I’m pleased now with the results. Here the Passmark 9.0 benchmark as uploaded onto their database (for more details, click the frame below):
I’ve been contemplating a PC upgrade for more than a year (see my post here). At first I considered staying with Intel and getting an i9-9900K CPU with integrated GPU on a Z390 motherboard.
Along came the AMD Ryzen 9 3900X that topped the benchmarks, including the Adobe Lightroom and Photoshop benchmarks (to be precise, it ranked #4 in the Adobe Lightroom benchmark, and a narrow #1 in the Adobe Photoshop benchmark). These good news about the AMD Ryzen 3900X were soon followed by reports about BIOS issues and VFIO incompatibility. At the very least, it looked like VGA passthrough was more challenging.
More than a year has passed since I’ve posted about building a new PC. So what is holding me back from the upgrade? Time and money are considerations, but not the reason.
On paper, the AMD Ryzen 9 has outperformed Intel in most if not all tasks. The Ryzen 9 3900X beats the Intel i9 9900K as well as the Intel i9 10900X in multi-threaded workloads. The Intel i9 9900K can barely hold its ground on single-threaded tasks. Numerous benchmarks have shown that AMD is a clear winner. Continue reading “Hardware upgrade or what’s holding me back?”
A year ago I wrote about the 2D graphics performance impact of the Windows 10 (1803) update inside a virtual machine. As it turned out, the performance impact was related to the Spectre vulnerability patch that Microsoft had introduced. However, the same patch had practically no performance impact on a Windows 10 bare-metal installation.