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That's why I'm >> pushing back so hard on using phys_addr_t or CPU addresses. >> >> See the CPU address is only valid temporary because the VF BAR is >> only a window into the device memory. > > I know, generally yes. > > But there should be no way that a VFIO VF driver in the hypervisor > knows what is currently mapped to the VF's BAR. The only way I can > make sense of what Xe is doing here is if the VF BAR is a static > aperture of the VRAM.. > > Would be nice to know the details. Yeah, that's why i asked how VFIO gets the information which parts of the it's BAR should be part of the DMA-buf? That would be really interesting to know. Regards, Christian. > >> What Simona agreed on is exactly what I proposed as well, that you >> get a private interface for exactly that use case. > > A "private" interface to exchange phys_addr_t between at least > VFIO/KVM/iommufd - sure no complaint with that. > > Jason