Re: Regression from 3.4.9 to 3.4.16 "stable" kernel

Ben Hutchings
2012-10-29T14:41:21Z

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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.

Ben.

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

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