Re: [PATCH] x86: revert "x86: Fix S4 regression"
From: Takao Indoh
Date: Mon Jul 23 2012 - 07:27:06 EST
(2012/07/23 19:00), Dave Young wrote:
> On 07/17/2012 11:15 AM, Takao Indoh wrote:
>> Hi Cong,
>> When I tested kdump with 3.5.0-rc6 kernel, I found a problem of kdump
>> kernel's panic in find_early_table_space().
>> init_memory_mapping: [mem 0x00000000-0x36ffafff]
>> Kernel panic - not syncing: Cannot find space for the kernel page tables
>> Pid: 0, comm: swapper Not tainted 3.5.0-rc6 #17
>> Call Trace:
>> [<ffffffff8158549b>] panic+0xb8/0x1c8
>> [<ffffffff8158565d>] ? printk+0x48/0x4a
>> [<ffffffff8157304c>] init_memory_mapping+0x46c/0x530
>> [<ffffffff818a73c7>] setup_arch+0x669/0xb0e
>> [<ffffffff8158565d>] ? printk+0x48/0x4a
>> [<ffffffff818a3a1f>] start_kernel+0x9b/0x34a
>> [<ffffffff818a332d>] x86_64_start_reservations+0x131/0x136
>> [<ffffffff818a341f>] x86_64_start_kernel+0xed/0xf4
>> In find_early_table_space(), a kernel tries to find free area below 512M
>> for pgtable using memblock_find_in_range, but it fails because kdump
>> kernel does not have enough free space below 512M due to the memmap
>> restriction. This is the memmap option specified against kdump kernel
>> when crashkernel=128M.
>> memmap=560K@64K memmap=130492K@770608K
>> Only 560KB area is available and it is not sufficient for pgtable (it
>> seems that about 1.8MB area is needed for pgtable). This problem is
>> fixed by your revert patch. I hope this patch gets merged.
> I can reproduce this issue as well, probably related to some x86 mm init
> commits, this alloc failure does not happen with reverting below commits:
Yeah, my result of bisect is as follows and at first I thought the
commit 722bc6 caused this regression.
722bc6b16771ed80871e1fd81c86d3627dda2ac8 is the first bad commit
Author: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Date: Mon Mar 5 15:05:13 2012 -0800
IIUC, this commit just fixes a bug of counting pgtable entries. As the
result, another problem came up to the surface. In the case of my
machine(16GB memory), before applying 722bc6, find_early_table_space()
requests about 12KB free area and it can be got from 560K@64K area
luckily. I think the size find_early_table_space() requests was a bug.
After the bug is fixed by the commit 722bc6, find_early_table_space()
requires 1.8MB area and it fails as I wrote.
>> Takao Indoh
>> (2012/06/12 14:21), Cong Wang wrote:
>>> From: Cong Wang <xiyou.wangcong@xxxxxxxxx>
>>> This reverts the following commit:
>>> commit 8548c84da2f47e71bbbe300f55edb768492575f7
>>> Author: Takashi Iwai <tiwai@xxxxxxx>
>>> Date: Sun Oct 23 23:19:12 2011 +0200
>>> x86: Fix S4 regression
>>> Commit 4b239f458 ("x86-64, mm: Put early page table high") causes a S4
>>> regression since 2.6.39, namely the machine reboots occasionally at S4
>>> resume. It doesn't happen always, overall rate is about 1/20. But,
>>> like other bugs, once when this happens, it continues to happen.
>>> This patch fixes the problem by essentially reverting the memory
>>> assignment in the older way.
>>> According to the previous discussion:
>>> it seems that so far the best solution is just reverting it.
>>> Takashi, could you help to test if the S4 regression is still
>>> there after this patch?
>>> Reported-by: CAI Qian <caiqian@xxxxxxxxxx>
>>> Cc: Dave Young <dyoung@xxxxxxxxxx>
>>> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
>>> Cc: Rafael J. Wysocki <rjw@xxxxxxx>
>>> Cc: Yinghai Lu <yinghai.lu@xxxxxxxxxx>
>>> Cc: Takashi Iwai <tiwai@xxxxxxx>
>>> Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
>>> arch/x86/mm/init.c | 3 ++-
>>> 1 files changed, 2 insertions(+), 1 deletions(-)
>>> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
>>> index bc4e9d8..7ab7975 100644
>>> --- a/arch/x86/mm/init.c
>>> +++ b/arch/x86/mm/init.c
>>> @@ -74,8 +74,9 @@ static void __init find_early_table_space(struct map_range *mr, unsigned long en
>>> #ifdef CONFIG_X86_32
>>> /* for fixmap */
>>> tables += roundup(__end_of_fixed_addresses * sizeof(pte_t), PAGE_SIZE);
>>> good_end = max_pfn_mapped << PAGE_SHIFT;
>>> base = memblock_find_in_range(start, good_end, tables, PAGE_SIZE);
>>> if (!base)
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