linux-kernel - Re: Regression from 3.4.9 to 3.4.16 "stable" kernel

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Date:	Mon, 29 Oct 2012 14:40:58 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Mark Lord <kernel@...savvy.com>, Yinghai Lu <yinghai@...nel.org>
Cc:	Willy Tarreau <w@....eu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jacob Shin <jacob.shin@....com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: Regression from 3.4.9 to 3.4.16 "stable" kernel

On Mon, 2012-10-29 at 10:22 -0400, Mark Lord wrote:
> On 12-10-29 02:46 AM, Willy Tarreau wrote:
> > On Mon, Oct 29, 2012 at 12:03:55AM -0400, Mark Lord wrote:
> >> My server here runs the 3.4.xx series of "stable" kernels.
> >> Until today, it was running 3.4.9.
> >> Today I tried to upgrade it to 3.4.16.
> >> It hangs in setup.c.
> >>
> >> I've isolated the fault down to this specific change
> >> that was made between 3.4.9 and 3.4.16.
> >> Reverting this change allows the system to boot/run normally again.
> >>
> >>
> >> --- linux-3.4.9/arch/x86/kernel/setup.c	2012-08-15 11:17:17.000000000 -0400
> >> +++ linux-3.4.16/arch/x86/kernel/setup.c	2012-10-28 13:36:33.000000000 -0400
> >> @@ -927,8 +927,21 @@
> >>
> >>  #ifdef CONFIG_X86_64
> >>  	if (max_pfn > max_low_pfn) {
> >> -		max_pfn_mapped = init_memory_mapping(1UL<<32,
> >> -						     max_pfn<<PAGE_SHIFT);
> >> +		int i;
> >> +		for (i = 0; i < e820.nr_map; i++) {
> >> +			struct e820entry *ei = &e820.map[i];
> >> +
> >> +			if (ei->addr + ei->size <= 1UL << 32)
> >> +				continue;
> >> +
> >> +			if (ei->type == E820_RESERVED)
> >> +				continue;
> >> +
> >> +			max_pfn_mapped = init_memory_mapping(
> >> +				ei->addr < 1UL << 32 ? 1UL << 32 : ei->addr,
> >> +				ei->addr + ei->size);
> >> +		}
> >> +
> >>  		/* can we preseve max_low_pfn ?*/
> >>  		max_low_pfn = max_pfn;
> >>  	}
> > 
> > For the record, it is this commit introduced in 3.4.16 :
> > 
> > commit efd5fa0c1a1d1b46846ea6e8d1a783d0d8a6a721
> > Author: Jacob Shin <jacob.shin@....com>
> > Date:   Thu Oct 20 16:15:26 2011 -0500
> > 
> >     x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.
> >     
> >     commit 1bbbbe779aabe1f0768c2bf8f8c0a5583679b54a upstream.
> >     
> >     On systems with very large memory (1 TB in our case), BIOS may report a
> >     reserved region or a hole in the E820 map, even above the 4 GB range. Exclude
> >     these from the direct mapping.
> >     
> >     [ hpa: this should be done not just for > 4 GB but for everything above the legacy
> >       region (1 MB), at the very least.  That, however, turns out to require significant
> >       restructuring.  That work is well underway, but is not suitable for rc/stable. ]
> >     
> >     Signed-off-by: Jacob Shin <jacob.shin@....com>
> >     Link: http://lkml.kernel.org/r/1319145326-13902-1-git-send-email-jacob.shin@amd.com
> >     Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> >     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > Willy
> 
> 
> Thanks, Willy.
> 
> I've also now downloaded linux-3.7.0-rc3, and it boots/runs without need for patching.
> So there's a fix somewhere in between that perhaps could also get backported to -stable.

Might well be:

commit 1f2ff682ac951ed82cc043cf140d2851084512df
Author: Yinghai Lu <yinghai@...nel.org>
Date:   Mon Oct 22 16:35:18 2012 -0700

    x86, mm: Use memblock memory loop instead of e820_RAM

However I'm not sure that this loop is correct either.  Yinghai, does
your version definitely iterate in increasing pfn order?  If not then
the max_pfn_mapped assignment must be conditional.

Ben.

-- 
Ben Hutchings
Humans are not rational beings; they are rationalising beings.

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