Re: [PATCH] x86: revert "x86: Fix S4 regression"

[Dave Young]

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:

bd2753b2dda7bb43c7468826de75f49c6a7e8965
722bc6b16771ed80871e1fd81c86d3627dda2ac8



> 
> Thanks,
> 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:
>> http://marc.info/?l=linux-kernel&m=133161674120253&w=2
>> 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);
>> -#endif
>> +
>>   	good_end = max_pfn_mapped << PAGE_SHIFT;
>> +#endif
>>   
>>   	base = memblock_find_in_range(start, good_end, tables, PAGE_SIZE);
>>   	if (!base)
>>



-- 
Thanks
Dave
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