On Tue, 23 Jun 2026 01:54:59 +0000
David Hu <[email protected]> wrote:
> Currently, `fill_sg_entry()` splits the scatterlist using `UINT_MAX`.
> This creates a non-page-aligned DMA length (`0xFFFFFFFF`) for the
> first entry, resulting in non-page-aligned DMA addresses for all
> subsequent entries.
There is a separate issue of whether this code is even needed at all.
Where can transfers over 2G (never mind 4G) actually come from.
The read, write and similar system calls limit transfers to INT_MAX
(even on 64bit) and a lot of driver code will need fixing it longer
lengths are allowed though.
io_uring better enforce the same limits.
So the transfers can come directly from userspace.
Not only that but you also need a single physically contiguous buffer.
Good luck allocating that!
Now maybe there are some peer-to-peer places where the large buffer
is device memory, but they will be unusual and probably need
special treatment anyway.
David
