Hi Finn,

FTR, here is the diff of the dmesg between good and bad:

    +initrd: 07f61166 - 08000000

This is wrong (note the 6 trailing zeros), as phys_to_virt() is not
working correctly yet (module_fixup() is called from paging_init()).

     Zone ranges:
       DMA      [mem 0x0000000007400000-0x0000007fffffffff]
       Normal   empty
     Movable zone start for each node
     Early memory node ranges
       node   0: [mem 0x0000000007400000-0x0000000007ffffff]
     Initmem setup node 0 [mem 0x0000000007400000-0x0000000007ffffff]
    -initrd: 00b61166 - 00c00000

This is correct (note the 5 trailing zeros).

    -pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
    -pcpu-alloc: [0] 0
     [...]
    +Unable to handle kernel access at virtual address (ptrval)
    +Oops: 00000000
    +Modules linked in:
    +PC: [<002c11be>] memcmp+0x2c/0x5c
    +SR: 2700  SP: (ptrval)  a2: 003bd560
    +d0: 0035eb83    d1: 07fffff8    d2: 002c1192    d3: 000000e6
    +d4: 000684e8    d5: 00447000    a0: 0000000c    a1: 07fffff4
    +Process swapper (pid: 0, task=(ptrval))
    +Frame format=7 eff addr=003bbfbc ssw=0505 faddr=07fffff4
    +wb 1 stat/addr/data: 0005 00447000 07401000
    +wb 2 stat/addr/data: 0005 000000e6 000684e8
    +wb 3 stat/addr/data: 0005 003bbfb4 002c1192
    +push data: 07401000 002c7d82 07401000 074a2cf4
    +Stack from 003bbfb4:
    +002c1192 000000e6 002c7d82 00428eda 07fffff4 0035eb7f 0000000c 00447000
    +000000e6 000684e8 00447000 07401000 074bec08 07401000 074a2cf4 07fffff0
    +00440406 00000000 00428322
    +Call Trace: [<002c1192>] memcmp+0x0/0x5c
    +[<002c7d82>] _printk+0x0/0x18
    +[<00428eda>] start_kernel+0x80/0x5b0
    +[<000684e8>] pcpu_alloc+0x88/0x3b4
    +[<00428322>] _sinittext+0x322/0x9b0

On Mon, Feb 27, 2023 at 7:30 AM Finn Thain <fth...@linux-m68k.org> wrote:
> On Mon, 27 Feb 2023, Michael Schmitz wrote:
> > I wonder whether Finn's memtest patch merely exposed another MM bug
>
> A kernel patch may be easier than a bootloader patch (even if this is a
> bootloader bug) particularly if it affects multiple platforms.
>
> A partial revert of my patch (below) will probably avoid the issue, but
> with the side effect that use of memtest will clobber the initrd.

Which we can avoid, by moving the ramdisk handling inside paging_init().

> The initrd and memtest features aren't usually needed together. At the
> time when I needed the memtest feature I did not have confidence in the
> hardeare. An initrd wasn't very useful at that point.
>
> diff --git a/arch/m68k/kernel/setup_mm.c b/arch/m68k/kernel/setup_mm.c
> index 3a2bb2e8fdad..92f1b9268dff 100644
> --- a/arch/m68k/kernel/setup_mm.c
> +++ b/arch/m68k/kernel/setup_mm.c
> @@ -326,6 +326,8 @@ void __init setup_arch(char **cmdline_p)
>                 panic("No configuration setup");
>         }
>
> +       paging_init();
> +
>  #ifdef CONFIG_BLK_DEV_INITRD
>         if (m68k_ramdisk.size) {
>                 memblock_reserve(m68k_ramdisk.addr, m68k_ramdisk.size);

Presumably something in memblock_reserve() relies on having
called paging_init() before?

I'll do some more debugging later today...

> @@ -335,8 +337,6 @@ void __init setup_arch(char **cmdline_p)
>         }
>  #endif
>
> -       paging_init();
> -
>  #ifdef CONFIG_NATFEAT
>         nf_init();
>  #endif
>


-- 
Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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