Re: [PATCH] ion: scatterlist offset not used for buffer map

[Laura Abbott]

On 04/07/2016 11:56 PM, John Einar Reitan 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);
>
> 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.

This patch should be re-sent when you have the RFC for the heap. Unless
there is a heap available in tree we don't really need this patch.

Thanks,
Laura