On Wed, 2014-07-02 at 17:53 +0200, Stefan Klug wrote: > Implementation details: > The patch only touches drivers/usb/core/devio.c. > In procy_do_submiturb(), it is checked if zerocopy is allowed. This is > currently a rough > check which compares the number of required pages to > ps->dev->bus->sg_tablesize. It seems to me that the check is per call, so using multiple calls one could still pin unlimited amounts of memory. > I don't know if there is more to check there. > Then the user memory provided inside the usbdevfs_urb structure is > pinned to > physical memory using get_user_pages_fast(). > All the user pages are added to the scatter-gather list and the logic > continues as before. How do you enforce the cache coherency rules? Also you don't have a fall back if get_user_pages_fast() returns less than requested. It seems to me that than you ought to fall back buffered IO. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
