Date: Mon, 29 Oct 2012 09:47:22 -0500
From: Jacob Shin <jacob.shin@amd.com>
To: Ben Hutchings <ben@decadent.org.uk>
CC: Mark Lord <kernel@teksavvy.com>, Yinghai Lu <yinghai@kernel.org>,
        Willy Tarreau <w@1wt.eu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        <stable@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@linux.intel.com>
Subject: Re: Regression from 3.4.9 to 3.4.16 "stable" kernel
Message-ID: <20121029144722.GA23217@jshin-Toonie>
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On Mon, Oct 29, 2012 at 02:40:58PM +0000, Ben Hutchings wrote:
> 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@amd.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@amd.com>
> > >     Link: http://lkml.kernel.org/r/1319145326-13902-1-git-send-email-jacob.shin@amd.com
> > >     Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
> > >     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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@kernel.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.

Hi, I believe these two commits in mainline should fix Alexander's failing
machien:

844ab6f993b1d32eb40512503d35ff6ad0c57030
f82f64dd9f485e13f29f369772d4a0e868e5633a

This thread has some more details:

https://lkml.org/lkml/2012/10/21/157

Sorry, and thanks!

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


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