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https://bugs.freedesktop.org/show_bug.cgi?id=6242
------- Additional Comments From [EMAIL PROTECTED] 2006-03-31 13:19 -------
(In reply to comment #5)
> Created an attachment (id=5123)
--> (https://bugs.freedesktop.org/attachment.cgi?id=5123&action=view) [edit]
> mach64-drm: DMA buffers for vertices - try 2
>
> enable test of register values in the vertex buffer.
It's good to see this driver getting some attention again, I'm sorry I don't
have time to help out with the code right now.
I wanted to point out that if you go this route (using client DMA buffers for
vertices), you'll need to unmap the buffers from userspace before verifying and
submitting them to make this secure. If you look at the CVS history, you'll see
that we actually used to use DMA buffers, but changed to the current method when
beginning the work to make the driver secure. We decided that copying the data
from client memory into a pool of unmapped DMA buffers in the kernel would be
faster than unmapping and re-mapping the buffers for each submit. Copying the
userspace data into DMA buffers allocated from the mapped pool was a stopgap
until we had a way to allocate unmapped buffers in the kernel for this purpose.
It's been a while since I looked at the code in detail, but the problem at the
time was a limitation of the DRM buffer management infrastructure. As I recall,
there wasn't an easy way to create two sets of DMA buffers, one mapped to
userspace, and one which wasn't mapped. You may want to look into the mailing
list archives for more discussion on this. I think that this was the last
remaining issue in securing the driver.
-Leif
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