Re: [Patch] min_low_pfn and max_low_pfn calcultion fix

From: Jay Lan <jlan_at_sgi.com>
Date: 2007-03-15 02:55:51
Jay Lan wrote:
> Magnus Damm wrote:
> [snip]
>>> I tested on 2.6.21-rc3 with DEBUG_VM turned on. The vanilla 2.6.21-rc3
>>> without Nan-hai's patch, panicked on bugcheck on free_initmem->free_page
>>> as predicted. We still need this patch.
>> Ok, thanks for testing. =)
>>
>>> However, the zero-size vmcore problem is back on SN. But that is a
>>> dfiffernet problem.
>> Argh, more problems...
> 
> I found the problem. It was the "elfcorehdr" introduced in 2.6.21-rc1.
> Without specifying it, the elfcorehdr_addr is initialized to
> ELFCORE_ADDR_MAX. Later, a check in reserve_elfcorehdr will fail:
>         if (elfcorehdr_addr >= ELFCORE_ADDR_MAX)
>                 return -EINVAL;
> 
> Is it supposed to be a physical address to store elf core header?
> If so, it is not possible for SN to provide a physical address at
> boot time, just like in the case of crashkernel=X@Y where Y is not used.

Sorry, the elfcorehdr parameter is provided to the kdump kernel by
kexec. The problem is in the reserve_elfcorehdr logic introduced in
2.6.21-rc1.

When booting up the kdump kernel, i observed a failure in
reserve_elfcorehdr. The below are my debugging messages:

elfcorehdr_addr=3027fe4000, ELFCORE_ADDR_MAX=ffffffffffffffff
Cannot locate EFI vmcore descriptor
reserve_elfcorehdr: vmcore descriptor size = 0
reserve_memory: FAIL to reserve reserve_elfcorehdr

- jay



> 
> Thanks,
>  - jay
> 
> 
>> / magnus
>> -
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Received on Thu Mar 15 02:54:45 2007

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