[BUG] 2.6.25-rc8-mm1 kernel panic while bootup on powerpc

[Badari Pulavarty]

On Wed, 2008-04-02 at 18:17 +1100, Michael Ellerman wrote:
> On Wed, 2008-04-02 at 12:38 +0530, Kamalesh Babulal wrote:
> > Andrew Morton wrote:
> > > On Wed, 02 Apr 2008 11:55:36 +0530 Kamalesh Babulal <kamalesh at linux.vnet.ibm.com> wrote:
> > > 
> > >> Hi Andrew,
> > >>
> > >> The 2.6.25-rc8-mm1 kernel panic's while bootup on the power machine(s).
> > >>
> > >> [    0.000000] ------------[ cut here ]------------
> > >> [    0.000000] kernel BUG at arch/powerpc/mm/init_64.c:240!
> > >> [    0.000000] Oops: Exception in kernel mode, sig: 5 [#1]
> > >> [    0.000000] SMP NR_CPUS=32 NUMA PowerMac
> > >> [    0.000000] Modules linked in:
> > >> [    0.000000] NIP: c0000000003d1dcc LR: c0000000003d1dc4 CTR: c00000000002b6ac
> > >> [    0.000000] REGS: c00000000049b960 TRAP: 0700   Not tainted  (2.6.25-rc8-mm1-autokern1)
> > >> [    0.000000] MSR: 9000000000021032 <ME,IR,DR>  CR: 44000088  XER: 20000000
> > >> [    0.000000] TASK = c0000000003f9c90[0] 'swapper' THREAD: c000000000498000 CPU: 0
> > >> [    0.000000] GPR00: c0000000003d1dc4 c00000000049bbe0 c0000000004989d0 0000000000000001 
> > >> [    0.000000] GPR04: d59aca40f0000000 000000000b000000 0000000000000010 0000000000000000 
> > >> [    0.000000] GPR08: 0000000000000004 0000000000000001 c00000027e520800 c0000000004bf0f0 
> > >> [    0.000000] GPR12: c0000000004bf020 c0000000003fa900 0000000000000000 0000000000000000 
> > >> [    0.000000] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
> > >> [    0.000000] GPR20: 0000000000000000 0000000000000000 0000000000000000 4000000001400000 
> > >> [    0.000000] GPR24: 00000000017d64b0 c0000000003d6250 0000000000000000 c000000000504000 
> > >> [    0.000000] GPR28: 0000000000000000 cf000000001f8000 0000000001000000 cf00000000000000 
> > >> [    0.000000] NIP [c0000000003d1dcc] .vmemmap_populate+0xb8/0xf4
> > >> [    0.000000] LR [c0000000003d1dc4] .vmemmap_populate+0xb0/0xf4
> > >> [    0.000000] Call Trace:
> > >> [    0.000000] [c00000000049bbe0] [c0000000003d1dc4] .vmemmap_populate+0xb0/0xf4 (unreliable)
> > >> [    0.000000] [c00000000049bc70] [c0000000003d2ee8] .sparse_mem_map_populate+0x38/0x60
> > >> [    0.000000] [c00000000049bd00] [c0000000003c242c] .sparse_early_mem_map_alloc+0x54/0x94
> > >> [    0.000000] [c00000000049bd90] [c0000000003c250c] .sparse_init+0xa0/0x20c
> > >> [    0.000000] [c00000000049be50] [c0000000003ab7d0] .setup_arch+0x1ac/0x218
> > >> [    0.000000] [c00000000049bee0] [c0000000003a36ac] .start_kernel+0xe0/0x3fc
> > >> [    0.000000] [c00000000049bf90] [c000000000008594] .start_here_common+0x54/0xc0
> > >> [    0.000000] Instruction dump:
> > >> [    0.000000] 7fe3fb78 7ca02a14 4082000c 3860fff4 4800003c e92289c8 e96289c0 e9090002 
> > >> [    0.000000] e8eb0002 4bc575cd 60000000 78630fe0 <0b030000> 7ffff214 7fbfe840 7fe3fb78 
> > >> [    0.000000] ---[ end trace 31fd0ba7d8756001 ]---
> > >> [    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
> > >>
> > > 
> > > int __meminit vmemmap_populate(struct page *start_page,
> > > 					unsigned long nr_pages, int node)
> > > {
> > > 	unsigned long mode_rw;
> > > 	unsigned long start = (unsigned long)start_page;
> > > 	unsigned long end = (unsigned long)(start_page + nr_pages);
> > > 	unsigned long page_size = 1 << mmu_psize_defs[mmu_linear_psize].shift;
> > > 
> > > 	mode_rw = _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_COHERENT | PP_RWXX;
> > > 
> > > 	/* Align to the page size of the linear mapping. */
> > > 	start = _ALIGN_DOWN(start, page_size);
> > > 
> > > 	for (; start < end; start += page_size) {
> > > 		int mapped;
> > > 		void *p;
> > > 
> > > 		if (vmemmap_populated(start, page_size))
> > > 			continue;
> > > 
> > > 		p = vmemmap_alloc_block(page_size, node);
> > > 		if (!p)
> > > 			return -ENOMEM;
> > > 
> > > 		pr_debug("vmemmap %08lx allocated at %p, physical %08lx.\n",
> > > 			start, p, __pa(p));
> > > 
> > > 		mapped = htab_bolt_mapping(start, start + page_size,
> > > 					__pa(p), mode_rw, mmu_linear_psize,
> > > 					mmu_kernel_ssize);
> > > =====>		BUG_ON(mapped < 0);
> > > 	}
> > > 
> > > 	return 0;
> > > }
> > > 
> > > Beats me.  pseries?  Badari has been diddling with the bolted memory code
> > > in git-powerpc...
> > 
> > One of the machines is the Power5 and another is PowerMac G5, on which the 
> > same kernel panic is seen.
> 
> Can you enable DEBUG_LOW in arch/powerpc/platforms/pseries/lpar.c, that
> should show what's happening in hpte_insert().
> 
> cheers
> 

Okay. Found it.

Root cause is:

mm-make-mem_map-allocation-continuous.patch
and its friends in -mm.

You have to call sparse_init_one_section() on each pmap and usemap
as we allocate - since valid_section() depends on it (which is needed
by vmemmap_populate() to check if the section is populated or not).
On ppc, we need to call htab_bolted_mapping() on each section and
we need to skip existing sections.

These patches tried to group all allocations together and then later
calls sparse_init_one_section() - which is not good :(

Please let me know, if its doesn't make sense - I will try to explain
better :)

Thanks,
Badari