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Re: [Qemu-devel] hmp interface for kdump compressed format


From: qiaonuohan
Subject: Re: [Qemu-devel] hmp interface for kdump compressed format
Date: Wed, 2 Apr 2014 09:54:45 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.5) Gecko/20120607 Thunderbird/10.0.5

Hello guys,

I have sent the patch, please check here:

http://lists.nongnu.org/archive/html/qemu-devel/2014-04/msg00018.html

On 03/27/2014 04:38 PM, Markus Armbruster wrote:
"address@hidden"<address@hidden>  writes:

On 03/27/2014 01:04 AM, Markus Armbruster wrote:
So something like adding

  dump_guest_memory_set_format<format>

  would be the only possible solution with the hmp code as
is. Correct?

  Yes, one possibility would be to make the dump command stateful (=
  compression format), and to add a new command
setting/getting that state.

  Another option would be to leave the current command intact,
and add an
  independent command that wouldn't take "begin", "end", nor
"paging", but
  would take compression format.

  Another possibility is to kill begin/length from the
  dump-guest-memory command.
  HMP is not stable, so if that's useful we can do it.

  AFAIK, kdump-compressed format can only be analyzed by crash-utility right
  now. ELF is big but we still need it, then begin/length will help us save
  time and space when only part of the memory is need.

  IMHO, a new HMP command will be a good choice and it is more simple than
  making dump format 'stateful'. I am not so clear about HMP, but I think
  the new HMP command can be 'dump-guest-memory-with-format', and still
  base on qmp_dump_guest_memory. If you guys like it, I will send a patch
  that add this command.
Paolo encouraged you to*break*  the existing HMP command instead of
adding a new one.  I'd like to second that.
.


Hello markus,

I have finish my patch as I stated in my last mail, but something is
wrong with my mail server, I have to wait a couple of days before
sending the patch. You said you prefer *breaking* the existing HMP
command. Since paging/begin/length is still usefull, would you please
give some reason and I will consider that.

I'm encouraging you to design a HMP command that gives you all you need.
Then call that dump-guest-memory, backward compatibility be damned.

Would

     dump-guest-memory [-p] filename [[format] begin length]

do?

An alternative could be two commands:

     dump-guest-memory filename [format [begin length]]
     dump-guest-memory-elf [-p] filename [begin length]

This bakes the restriction "paging, begin and length work only with
format 'elf'" into the interface.  Not sure that's a good idea, but I'm
leaving that to folks who actually know something about this dumping
business.

If you can find better command names, go right ahead.  You could pick
names that avoid incompatible change.  I care about avoiding
incompatible change to exotic HMP commands even less (a lot less, in
fact) than about naming of exotic HMP commands.

.



--
Regards
Qiao Nuohan



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