Subject: Re: 2.6.23 boot failures on x86-64.
From: Zou Nan hai <nanhai.zou@intel.com>
To: Martin Ebourne <martin@zepler.org>
Cc: Dave Jones <davej@redhat.com>, Andi Kleen <ak@suse.de>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Suresh Siddha <suresh.b.siddha@intel.com>, stable@kernel.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>
In-Reply-To: <1193810651.817.14.camel@linux-znh>
References: <20071029175014.GH7793@redhat.com>
	 <200710291918.43869.ak@suse.de> <20071029184747.GB1650@redhat.com>
	 <200710292003.09317.ak@suse.de>  <20071029194311.GE1650@redhat.com>
	 <1193692862.3133.14.camel@avenin.ebourne.me.uk>
	 <1193810651.817.14.camel@linux-znh>
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Date: 31 Oct 2007 14:19:19 +0800
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On Wed, 2007-10-31 at 14:04, Zou Nan hai wrote:
> On Tue, 2007-10-30 at 05:21, Martin Ebourne wrote:
> > On Mon, 2007-10-29 at 15:43 -0400, Dave Jones wrote:
> > > On Mon, Oct 29, 2007 at 08:03:09PM +0100, Andi Kleen wrote:
> > >  > >  > But if allocating bootmem >4G doesn't work on these systems
> > >  > >  > most likely they have more problems anyways. It might be better
> > >  > >  > to find out what goes wrong exactly.
> > >  > > Any ideas on what to instrument ?
> > >  > 
> > >  > See what address the bootmem_alloc_high returns; check if it overlaps
> > >  > with something etc.
> > >  > 
> > >  > Fill the memory on the system and see if it can access all of its memory.
> > > 
> > > Martin, as you have one of the affected systems, do you feel up to this?
> > 
> > Faking a node at 0000000000000000-000000001fff0000
> > Bootmem setup node 0 0000000000000000-000000001fff0000
> > sparse_early_mem_map_alloc: returned address ffff81000070b000
> > 
> > My box has 512MB of RAM.
> > 
> > Cheers,
> > 
> > Martin.
> 
> Oops, sorry,
> seem to be a mistake of me.
> I forget to exclude the DMA range.
> 
> Does the following patch fix the issue?
> 
> Thanks
> Zou Nan hai
> 
> --- a/arch/x86/mm/init_64.c	2007-10-31 11:24:11.000000000 +0800
> +++ b/arch/x86/mm/init_64.c	2007-10-31 12:31:02.000000000 +0800
> @@ -731,7 +731,7 @@ int in_gate_area_no_task(unsigned long a
>  void * __init alloc_bootmem_high_node(pg_data_t *pgdat, unsigned long size)
>  {
>  	return __alloc_bootmem_core(pgdat->bdata, size,
> -			SMP_CACHE_BYTES, (4UL*1024*1024*1024), 0);
> +			SMP_CACHE_BYTES, (4UL*1024*1024*1024), __pa(MAX_DMA_ADDRESS));
>  }
>  
>  const char *arch_vma_name(struct vm_area_struct *vma)
> 
> 
> 
>  

Please ignore the patch, the patch is wrong.

However I think the root cause is when __alloc_bootmem_core fail to
allocate a memory above 4G it will fall back to allocate from the lowest
page. 
Then happens to be allocated in DMA region sometimes...

Since this code path is dead, I am OK to revert the patch.

Suresh and I will check the CONFIG_SPARSE_VMEMMAP path.
Thanks
Zou Nan hai


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