Am 12.03.2013 14:08, schrieb Prabhu nath: > > > On Sun, Mar 10, 2013 at 11:30 PM, Christoph Seitz <c.seitz@xxxxxxxx > <mailto:c.seitz@xxxxxxxx>> wrote: > > Hi all, > > I have some problems allocation Memory the right way and use it in my > kernel module. > > I use a char device for reading and writing from/to a pcie dma card. > Especially the read function makes me some headache. The user allocates > some memory with posix_memalign and call the read function on the > device, so that the devices knows where to write to. My driver now uses > get_user_pages() to pin the user pages. The memory has never been > written or read by the user, so it's not yet in the RAM, right? And > get_user_pages returns a valid number of pages, but for every page the > same struct. (respectively the same pointer). Is there any way to ensure > that the user pages are in the ram and get_user_pages returns a valid > page array? > > > If you know the RAM physical address range you can figure out by doing > the following > *page_to_pfn(page_ptr) << 12*; > where page_ptr is a struct page * returned by get_user_pages(). > *page_to_pfn()* will return the pfn of the corresponding page frame > and left shifting by 12 bits will give you page frame base address. Maybe my description was a little bit misleading. I have the problem, that if I don't write to that allocated memory in the user application, I won't get any valid pages from get_user_pages. The reason seems to be, that thees pages never got faulted and so the user memory never gets a page frame. Is there any chance for a kernel module to force a page fault or to assign the user memory a page frame? I found out, if I use the force flag with get_user_pages, the pages get faulted, but there has to be a nicer way than using the force flag. Regards, Chris _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
