One of the most important parts of your build will be the guest GPU, and selecting one with high compatibility that fits your needs can be difficult. Here’s a quick rundown on what to look for.
What’s a Guest GPU?
It’s the graphics card that you pass over to your virtual machine to enable 3D acceleration and Gaming. Ideally you would be able to share it between the host and guest, but we don’t live in a perfect world, so you (with a few new and very expensive exceptions) need two GPUs, one for each OS. On systems with an iGPU, this means you only need to buy one discreet card, but on AMD and intel HEDT platforms, you’ll need a Host card as well.
Miners will buy up a lot of models as soon as they hit the shelves, so even highly compatible models tend to be scarce at a certain level of performance. Generally, though, there are 2 routes you can take for effectively selecting a Guest GPU:
Nvidia — all the cards are “broken”
Luckily, they’re all broken in the same way. Nvidia’s drivers will abort with an error if you try loading them in a VM with a consumer card attached. There’s a well documented workaround though, and with 5 extra lines in your XML, you can get them up and running.The rule of thumb with consumer Nvidia cards is that they all work with a little tweaking, more or less.
You can also drop a lot more money on a quadro and skip editing your xml, but we don’t recommend it.
AMD — some work, some just plain don’t
AMD has no such driver restriction for their consumer cards, which means (at least in theory) that they should “just work.” And a lot of them do. The trouble is, some of the AiB partners’ BIOS modifications don’t play well with KVM. A badly put together vBIOS can harm or even completely stop a passthrough gaming VM from working as intended. There are several bugs caused by this issue, that are collectively known as “The AMD Reset Bug.” There are 2 levels of severity:
- [*] Hang on Crash — The VM will work normally, but if it crashes during normal use, it will fail to reinitialize and will only become available again on system reboot. This is the less severe of the two levels, and may not affect the user at all if they aren’t overclocking or experiencing other system instability.
- [**] Hang on Reboot — The VM will work normally, but will fail to reinitialize after it is shut off, only becoming available when the host reboots. This level of the bug will make the card incredibly inconvenient to use for passthrough gaming.
There are workarounds that do work for some cards, but they aren’t as well documented or tested as the Nvidia Fixes, so we attempt to curate bug-free cards as best we can on this page.