Re: [PATCH 6.10 000/809] 6.10.3-rc3 review

[Guenter Roeck <linux@roeck-us.net>]

On 8/8/24 11:19, Linus Torvalds wrote:
> On Thu, 8 Aug 2024 at 10:48, Thomas Gleixner <tglx@linutronix.de> 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