On Tue, Dec 14, 2010 at 10:06 AM, Jerome Glisse <j.gli...@gmail.com> wrote:
> On Mon, Dec 13, 2010 at 9:04 PM, Jammy Zhou <jammy.z...@linaro.org> wrote: > > > > > > On Tue, Dec 14, 2010 at 12:11 AM, Jerome Glisse <j.gli...@gmail.com> > wrote: > >> > >> On Mon, Dec 13, 2010 at 10:18 AM, Arnd Bergmann <a...@arndb.de> wrote: > >> > On Monday 13 December 2010, Jammy Zhou wrote: > >> >> On Mon, Dec 13, 2010 at 4:45 AM, Linus Walleij > >> >> <linus.wall...@linaro.org>wrote: > >> >> > >> >> > On 11 December 2010 22:41, Arnd Bergmann <a...@arndb.de> wrote: > >> >> > > >> >> > * amd-gpu -- a single but huge driver for the GPU. As is normally > the > >> >> >> case with GPU drivers, we can expect long discussions > >> >> >> before it will get considered for mainline > >> >> >> 4 patches > >> >> >> 98 files changed, 278321 insertions(+), 0 deletions(-) > >> >> >> > >> >> > > >> >> > Just out of curiosity, following the discussion between Dave Airlie > >> >> > and Codeaurora this summer re GPU driver shims. > >> >> > > >> >> > Is the AMD GPU exposing all functionality in its kernel driver or > >> >> > is there some userspace blob somewhere with lots of e.g. GL > >> >> > goodies? > >> >> > > >> >> All the functionality for the kernel driver of AMD GPU Z430/Z160 (now > >> >> belongs to Qualcom) is exposed. But we need accompanied userspace > >> >> library to > >> >> call these functionality (buffer management, command submission, > ...). > >> > > >> > Who owns these components? If it's closed source, the only options we > >> > have are lobbying for complete release of the specs for a > >> > reimplementation > >> > or reverse-engineering the drivers, which may at least get easier with > >> > a user space driver than it would be with a kernel driver. > >> > > >> > Until there is a solution with an open source user space part, I would > >> > suggest that the driver better be dropped from the Freescale BSP and > >> > we should at least not waste time reviewing it. > >> > > >> > Arnd > >> > >> From a quick look it also seems that the API exposed to userspace > >> would allow easy abuse of the GPU to access any system ram. There is a > >> reason we do expensive command checking in the other amd gpu driver > >> (drivers/gpu/drm/radeon/*cs.c files) > > > > No, the memory used by the GPU is reserved at boot time, so I think there > is > > no such a problem. > > > >> > >> Cheers, > >> Jerome > > > > > > This isn't about what's reserved, this is about GPU capacity, if the > GPU is isolated through an IOMMU and the GPU can't reprogram it then > fine. But if not, then it's easy to abuse packet to reprogram the GPU > GART (either by reprogramming GART register or by overwritting GART > table) to point to any system ram. > For non-PCI GPU in embedded world, there is no GART concept. Besides, the GPU MMU is disabled currently for some hardware problem. > > Cheers, > Jerome >
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