On 2/16/24 07:13, Charlie Jenkins wrote:
On Thu, Feb 15, 2024 at 10:09:42PM -0800, Guenter Roeck wrote:
On 2/15/24 21:54, Helge Deller wrote:
[ ... ]
Can you please give a pointer to this test code?
I'm happy to try it on real hardware.
You should also see the problem if you use v7 of Charlie's checksum
unit test fixes.
I submitted the qemu fix (or at least what I think the fix should be)
a couple of minutes ago.
https://patchwork.kernel.org/project/qemu-devel/patch/20240216053415.2163286-1-linux@xxxxxxxxxxxx/
It is quite easy to show that carry is always set after executing ldd
on an unaligned address. That is also why I know for sure that the
problem is not seen with ldw on unaligned addresses.
Interesting.
Ultimately it wasn't surprising, with the unusual carry bit
implementation on hppa. The upper 8 carry bits were not masked
correctly when returning from a trap or interrupt.
Tangential question, but why does Linux need to save and restore the PSW
if that is already handled by the hardware? I am missing something.
e.g. for task switching.
Helge
