On 24/08/2023 5:49 pm, Matthew Wilcox wrote:
On Thu, Aug 24, 2023 at 05:39:38PM +0100, Robin Murphy wrote:
As for >2GB segments, we've certainly seen cases of users mapping absurdly
large buffers and overflowing dma_length[2], so I would imagine it's only
the improbability of allocating that much physically-contiguous memory which
keeps individual segment lengths from getting up to UINT_MAX ;)
With a 32-bit kernel though? ;-)
Oh, indeed, that's more of a challenge... I guess take an LPAE system
with enough RAM, run VMSPLIT_3G and convince a dma-buf heap to let you
import ~2.5GB of contiguous highmem for some kind of in-place media
processing, maybe? Not exactly 4, but still more than 2. In principle :D
Robin.
