On Thu, Apr 7, 2016 at 11:56 PM, John Einar Reitan <john.reitan@xxxxxxxxxxxx> wrote: > On Thu, Apr 07, 2016 at 12:37:50PM -0700, Laura Abbott wrote: >> On 04/07/2016 04:29 AM, John Einar Reitan wrote: >> > ion's default user/kernel page mapping code don't honor the offset >> > option for scatterlists. It uses sg_page and expect the whole page to be >> > mapped, while the offset could dictate an offset within a large page. >> > >> > sg_phys correctly accounts for the offset, so should be used instead. >> > >> >> Can you be more specific about which heap and which allocation pattern >> is exposing this bug? > > The heap that exposed the bug is one I'm developing and will be posting > as a RFC soon. It uses compound pages and an sub-divides it into surface > buffers. The ion buffers are configured to hold sgl's with the compound > page and the correct offset of the buffer, via > sg_set_page(.., compound_page, .., offset_of_logical_buffer); I don't think this is right. A compound_page still has a page struct for every page, you should be passing the page struct where your data starts. Using an offset > PAGE_SIZE is going to break lots of places, for example anywhere that uses kmap(sg_page(sg)). > sg_phys/sg_virt includes this offset, but if you poke the sg and extract > the page with sg_page yourself you must include this offset in your > calculations too. _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
