On Tue, Nov 13, 2018 at 05:38:53PM +0200, Yehezkel Bernat wrote: > Good point. But I thought about per-TBT-device decision. If the platform is > configured for IOMMU+"user" security level, while approving the device the user > may want to set also in which IOMMU group to put all the PCIe devices connected > to it. The same goes if kernel is supposed to auto-approve such devices based on > an internal table. The point is that we can think on a configuration where the > devices aren't tunneled yet and the decision about IOMMU can still be changed. Right, some of these systems have security level set to "user" so there we could have a way to put the device into passthrough mode before it appears on the PCIe bus. That would require some sort of API on the IOMMU side, though. > As you mentioned this isn't the common configuration anyway, so it probably > doesn't worth all this hassle. AFAIK mixing the two is not something they are going to be supporting in Windows so I would not expect it to be common. I think the ultimate goal is to move away from security levels towards IOMMU DMA protection so in future I would expect more and more systems with IOMMU enabled + security level set to "none". So I agree with you that it probably is not worth doing at least without having more data about real performance issues around this. ;-)
