I used to work on Myrinet HPC NICs many years ago, and the ability for a PCI(e) device to access any memory by user virtual address was a desirable feature. I

I used to work on Myrinet HPC NICs many years ago, and the ability for a PCI(e) device to access any memory by user virtual address was a desirable feature. I believe that Quadrics did this first using a patched version of DEC OSF/1 (UNIX, Tru64, whatever you want to call it), where they hooked into the kernel pmap (page table) code, and sync'ed the page tables with their NIC. That way the NIC could do the virtual to physical translations, and know if a virtual memory address was backed by a physical page. What Nvidia is doing here sounds similar. Does linux provide such primitives now?