On Tue, Apr 25, 2023 at 04:12:05AM -0400, Michael S. Tsirkin wrote: > In theory, absolutely. In practice modern virtio devices are ok, > the reason we are stuck supporting old legacy ones is because legacy > devices are needed to run old guests. And then people turn > around and run a new guest on the same device, > for example because they switch back and forth e.g. > for data recovery? Or because whoever is selling the > host wants to opt for maximum compatibility. > > Teaching all of linux to sometimes use dma and sometimes not > is a lot of work, and for limited benefit of these legacy systems. It's not like virtio is the only case where blindly assuming your can use DMA operations in a higher layer is the problem..
