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The downside is that the host kernel now puts more > trust in the user VMM, so my preference would be to keep this in the > vfio driver. Or we can do both, vfio-pci allows the relaxation, the VMM > tells KVM to go for a more relaxed stage 2 via an ioctl(). What is the point? We'd need a use case for why the VMM should have the ability to create a more restrictive MMIO mapping. I can't think of one. So I'd go the other way, if someday we find out we need more restrictive then the VMM should ask for more restrictive (not weirdly ask for less restrictive) Jason