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>> 2) shrinking GMEMFD equals to VM memory unplug and VMM is going to >> handle it. > > The VMM is outside of the kernel's effective TCB. Assuming the VMM will always > do the right thing is a non-starter. Right. But, say, for 1), VMM does not the right thing and skips on PSC - the AMD host will observe IOMMU fault events - noisy but harmless. I wonder if it is different for others though. Truncating gmemfd is bad, is having gmemfd->iommufd notification going to be enough for a starter? Thanks, -- Alexey