On Fri, 9 Sep 2022, Juergen Gross wrote: > On 09.09.22 04:11, Stefano Stabellini wrote: > > Adding more people in CC > > > > On Thu, 8 Sep 2022, Stefano Stabellini wrote: > > > Hi Juergen, > > > > > > A colleague is seeing a failure on x86 in Linux Dom0. The failure is > > > pin_user_pages_fast with addresses that correspond to foreign memory > > > pages: > > > > > > - QEMU maps a domU address using dma_memory_map (xen_map_cache) > > > - QEMU calls an IOCTL to the TEE subsystem with the Virtual Address > > > returned by dma_memory_map > > > - Linux tee_shm_register->pin_user_pages_fast Returns -14 - > > > drivers/tee/tee_shm.c > > > > > > Once upon a time it used to be the case that get_user_pages_fast would > > > fail on Xen because we didn't have a struct page corresponding to > > > foreign memory mappings. But that hasn't been the case for years now. > > > > > > Any other ideas why it would fail? > > I think we can expect that access_ok() isn't failing. > > I assume the mapping was done allowing writes (sorry for paranoia mode)? I was told it was verified: QEMU could read and write to the VA returned by dma_memory_map. From /proc/<qemu-pid>/maps, the VA assigned after the mapping is pointing to /dev/xen/privcmd.
> Other than that I'm not having enough memory management skills. It might be > related to mmap()-ed foreign pages having _PAGE_SPECIAL set, though. Do we still set PAGE_SPECIAL for foreign mapped pages? It looks like it is not there anymore? If PAGE_SPECIAL is not there, then they really should look like regular pages?
