On Thu, Jun 25, 2020 at 10:11:28AM +0200, Thomas Ruf wrote: > > > On 25 June 2020 at 02:42 Dave Jiang <dave.jiang@xxxxxxxxx> wrote: > > > > > > > > > > On 6/21/2020 12:24 AM, Vinod Koul wrote: > > > On 19-06-20, 16:31, Dave Jiang wrote: > > >> > > >> > > >> On 6/19/2020 3:47 PM, Federico Vaga wrote: > > >>> Hello, > > >>> > > >>> is there the possibility of using a DMA engine channel from userspace? > > >>> > > >>> Something like: > > >>> - configure DMA using ioctl() (or whatever configuration mechanism) > > >>> - read() or write() to trigger the transfer > > >>> > > >> > > >> I may have supposedly promised Vinod to look into possibly providing > > >> something like this in the future. But I have not gotten around to do that > > >> yet. Currently, no such support. > > > > > > And I do still have serious reservations about this topic :) Opening up > > > userspace access to DMA does not sound very great from security point of > > > view. > > > > What about doing it with DMA engine that supports PASID? That way the user can > > really only trash its own address space and kernel is protected. > > Sounds interesting! Not sure if this is really needed in that case... > I have already implemented checks of vm_area_struct for contiguous memory or even do a get_user_pages_fast for user memory to pin it (hope that is the correct term here). Of course i have to do that for every involved page. FWIW there is a new pin_user_pages_fast()/unpin_user_page() interface now. Ira > But i will do some checks if my code is really suitable to avoid misusage. > > Best regards, > Thomas
