On 8/8/24 11:19, Linus Torvalds wrote:
On Thu, 8 Aug 2024 at 10:48, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
Here is the disassembly from my latest crashing debug kernel which
shifts it up a couple of pages. Add 0x10 or sub 0x20 to make it work.
Looks like I was off by an instruction, it's the 28th divide-step (not
29) that does the page crosser:
4121dffc: 0b 21 04 41 ds r1,r25,r1
4121e000: 0b bd 07 1d add,c ret1,ret1,ret1
but my parisc knowledge is not good enough to even guess at what could go wrong.
And I have no actual reason to believe this has *anything* to do with
an itlb miss, except for that whole "exact placement seems to matter,
and it crosses a page boundary" detail.
None of this makes sense. I think we'll have to wait for Helge. It's
not like parisc is a huge concern, and for all we know this is all a
qemu bug to begin with.
Copying Richard Henderson who recently made a number of changes to the
parisc/hppa qemu implementation (which unfortunately didn't fix the problem).
Guenter
