CONFIG_PIN_TLB and telnet problems

[Paul Mackerras]

Dan Malek writes:

> As I mentioned in the first message, I suspect the problem is with the
> multiple mapping/access of data in the pinned and remapped areas.  Linux
> tends to allocate memory from the high end down, so if you consistent_alloc()
> some space on large memory systems, you are just remapping the attributes
> of a page.  If you do this on memory that is also covered by a large page,
> sometimes you will get the access through this large page, and others through
> an alternate mapping, which I believe confuses the MMU/cache with different
> attributes (which I was assured wouldn't cause problems on 4xx).

We have reproduced the problem using a ramdisk root and loopback, with
the ethernet disabled, so the only I/O device that is active is the
serial port, which doesn't use DMA.  So it doesn't look like it is
anything to do with DMA or with consistent_alloc.

Paul.

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/