Hi Mike, On Tue, Jun 18, 2019 at 8:10 AM Mike Rapoport <[email protected]> wrote: > On Mon, Jun 17, 2019 at 10:00:32PM +0200, Geert Uytterhoeven wrote: > > On Thu, May 16, 2019 at 8:03 AM Mike Rapoport <[email protected]> wrote: > > > These pacthes replace DISCONTIGMEM with SPARSEMEM on m68k for systems with > > > !SINGLE_MEMORY_CHUNK set. > > > > > > With SPARSEMEM there is a single node for the entire physical memory and > > > to > > > cope with holes in the physical address space it is divided to sections of > > > up to 16M. > > > > > > Each section has it's own memory map which size depends on actual > > > populated > > > memory. > > > > > > The section size of 16M was chosen pretty much arbitrarily as I couldn't > > > find specs for systems with e.g. Zorro memory extensions.
> > Unfortunately it crashes on my Amiga, cfr. the logs below.
> >
> > Then I realized the "section size of 16M". My Amiga has a single block
> > of 12 MiB of FastRAM at 0x07400000, which is not aligned to 16 MiB.
> > (Yes, base address of motherboard RAM is 0x08000000 - ramsize ;-)
> >
> > I've tried:
> >
> > -#define MAX_PHYSMEM_BITS 32
> > -#define SECTION_SIZE_BITS 24
> > +#define MAX_PHYSMEM_BITS 30
> > +#define SECTION_SIZE_BITS 22
> >
> > but that doesn't seem to make a difference.
> >
> > Do you have a clue? Thanks!
>
> Not really, at least yet.
> Can you please send the entire log with
>
> "mminit_loglevel=4 memblock=debug debug"
>
> in the command line?
Attached, with debug_boot_weak_hash added, which reveals it's a real
NULL (=0x0) pointer dereference.
Looking at the disassembly, it happens in clear_page().
Call chain:
get_page_from_freelist()
prep_new_page()
clear_highpage()
void *kaddr = kmap_atomic(page);
clear_page(kaddr);
get_page_from_freelist() verifies page is non-zero before calling
prep_new_page(), so it must be the kmap_atomic() that returns NULL.
kmap_atomic() basically does page_address(page).
As m68k defines WANT_PAGE_VIRTUAL, that evaluates to page->virtual,
which I assume to be NULL.
Is there a call to set_page_address() missing in the sparsemem code?
Questions:
1. Why does it work on Atari/ARAnyM?
2. Why does it work on SPARC64, which also uses WANT_PAGE_VIRTUAL
and has SPARSEMEM support? (arc uses WANT_PAGE_VIRTUAL, but no
SPARSEMEM)
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
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
dmesg-5.2.0-rc5-amiga-nomod-01404-gf5057647889105fe.2
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