Re: [Qemu-devel] [Question] dump memory when host pci device is used by guest

[Avi Kivity]

On 10/25/2011 10:35 AM, Paolo Bonzini wrote:
> On 10/25/2011 10:23 AM, Avi Kivity wrote:
>> On 10/25/2011 10:06 AM, Wen Congyang wrote:
>>> Hi, Avi Kivity, Dave Anderson
>>>
>>> I have two questions about it:
>>>
>>> 1. How to know the guest's physical base address in qemu?
>>
>> In fact, it's impossible.
>>
>> Perhaps crash can scan through the core looking for a signature.  Need
>> to be careful since multiple signatures may be detected (a kdump kernel,
>> a kernel image in pagecache, or a nested guest).
>
> Crash uses a heuristic based on the IDT base to identify the base from
> migrate-to-file output.  It also needs CR3 in order to read from
> virtual address.

Does elf not store cr3?  Perhaps a note with the contents of the
privileged cpu registers is needed.

How will gdb cope with module sections?  They are virtually contiguous
but physically scattered.  AFAICT gdb doesn't do translations itself. 
The kernel proper can be handled with a simple offset, but modules cannot.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.