[Crash-utility] Re: [PATCH 1/2] Add x86_64 linux-2.6.27 support: Catch up the PAGE_OFFSET change.

[Dave Anderson]

Ken'ichi Ohmichi wrote:
> Hello Dave,
> 
> Dave Anderson wrote:
> 
>>>I think that a new virtualization_init() function is a good idea.
>>>
>>>How about checking whether "Xen" exists in PT_NOTE section of an vmcore
>>>at virtualization_init()? I feel that it is safer than reading a xen_start_info
>>>pointer.
>>>
>>>$ readelf -n vmcore
>>>Notes at offset 0x00000120 with length 0x00001388:
>>>  Owner         Data size       Description
>>>  CORE          0x00000150      NT_PRSTATUS (prstatus structure)
>>>  Xen           0x00000020      Unknown note type: (0x01000002)  <----- HERE
>>>  CORE          0x00000150      NT_PRSTATUS (prstatus structure)
>>>  Xen           0x00000020      Unknown note type: (0x01000002)  <----- HERE
>>>  Xen           0x00000050      Unknown note type: (0x01000001)  <----- HERE
>>>  VMCOREINFO_XEN                0x00000fe4      Unknown note type: (0x00000000)
>>>$
>>
>>Well there may be a couple issues with that approach.  First, we need
>>a way to handle/recognize it on live systems. And second, I believe we'll need
>>a way to differentiate a pv_ops/xen kernel from a "dedicated" xen kernel.
>>And my guess is that the vmcore notes will not differentiate between the
>>two "flavors" of xen kernel (unless there's an entry in the VMCOREINFO_XEN
>>that will somehow differentiate the two).
> 
> 
> Thank you for the good comment. I understand your plan, and I think it is
> better than mine.

Yeah, the more I look into it, the more it appears that support for
pv_ops/xen (as well as the other pv_ops clients) are going to require
significant changes.

For now, only "traditional xen" will be supported, and when pv_ops/xen
comes online, we'll take a look at how to merge support for it.

Here's my initial update to your patch -- it simply recognizes pv_ops
kernels, and  disallows the setting of the ARCH_XEN in that case.

Dave






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