Re: Kernel versions 6.x don't boot on Amiga 4000

[Mike Rapoport <rppt@kernel.org>]

Hi,

On Mon, Feb 27, 2023 at 10:42:34PM +1300, Michael Schmitz wrote:
> Hi Geert,
> 
> adding Mike Rapoport to the recipient list who would know whether
> memblock_reserve() relies on paging_init() having run.
> 
> Cheers,
> 
> 	Michael
> 
> Am 27.02.2023 um 21:26 schrieb Geert Uytterhoeven:
> > 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 <fthain@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?

memblock_reserve() does not rely on paging_init() as it operates on
physical addresses and it does not care if memory was already registered.
 
What does rely on paging_init() it's phys_to_virt() in the line after
memblock_reserve():

		initrd_start = (unsigned long)phys_to_virt(m68k_ramdisk.addr);
		initrd_end = initrd_start + m68k_ramdisk.size;

So to have both memtest and initrd we'd need something like

	memblock_reserve(m68k_ramdisk.addr, m68k_ramdisk.size);

	paging_init() {
		/* setup page tables and memblock */
		early_memtest();
	}

	initrd_start = (unsigned long)phys_to_virt(m68k_ramdisk.addr);

or 

	paging_init(); /* without early_memtest() */

	memblock_reserve(m68k_ramdisk.addr, m68k_ramdisk.size);
	initrd_start = (unsigned long)phys_to_virt(m68k_ramdisk.addr);
	
	early_memtest();


> > 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
> > > 
> > 
> > 

-- 
Sincerely yours,
Mike.