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

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Date:	Mon, 29 Oct 2012 07:46:43 +0100
From:	Willy Tarreau <w@....eu>
To:	Mark Lord <kernel@...savvy.com>
Cc:	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, 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

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