A fix is in the works for AMD Ryzen users who have encountered Linux issues with virtualization when trying to set up passthrough support for a graphics card to allow the virtual machine direct access to the GPU. When NPT (Nested Page Tables) are enabled, performance can become severely degraded.



Mailing list post by Geoffrey McRae: “I have identified the issue! With NPT enabled, I am now getting near bare-metal performance with PCI passthrough. The issue was with some stubs that have not been properly implemented. I will clean my code up and submit a patch shortly. This is a 10-year-old bug that has only become evident with the recent ability to perform PCI passthrough with dedicated graphics cards. I would expect this to improve performance across most workloads that use AMD NPT.”

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Source: [H]ardOCP – AMD Ryzen NPT Fix Discovered for Better Passthrough Graphics Performance