Re: [Qemu-devel] [RFC][PATCH 09/16 v6] introduce a new monitor command 'dump' to dump guest's memory

[Eric Blake <eblake@redhat.com>]

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On 02/17/2012 01:52 AM, Wen Congyang wrote:
> At 02/15/2012 01:59 AM, Jan Kiszka Wrote:
>> On 2012-02-09 04:28, Wen Congyang wrote:
>>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>

<snip several kilobytes>

>>> +static DumpState *dump_init(int fd, Error **errp)
>>> +{
>>> +    CPUState *env;
>>> +    DumpState *s = dump_get_current();
>>> +    int ret;
>>> +
>>> +    vm_stop(RUN_STATE_PAUSED);
>>
>> I would save the current vm state first and restore it when finished.
> 
> There is no API to get current vm state. If you want this feature, I will
> add API to get it.
> 
> Thanks
> Wen Congyang

<snip several kilobytes>

Maybe it's just me, and you can ignore me if I'm speaking out of turn
for expressing my views on list netiquette, but...

I get frustrated by lengthy messages that are heavily re-quoted versions
of earlier versions, with only a very little new content embedded in the
middle where I have to hunt for it.  There's nothing wrong with using
the Delete key to trim replies down to relevant portions, which reduces
the bandwidth of the list engine as well as reduces the time spent in
reviewing email exchanges.

/me returns back to lurk mode, but with one additional observation:

There are other APIs where qemu has ended up pausing the domain and not
restoring things back to running when done, and where libvirt has had to
track existing state prior to starting actions in order to manually fix
things after the fact (see libvirt's qemudDomainCoreDump as a wrapper
around migration to file, for an example).  If we do things right in
this new DumpState API, we may want to decide to fix other monitor
commands to use the same mechanism (it won't offload any of the burden
from libvirt, which must still correctly interact with older qemu, but
would make life nicer for clients that can assume the saner semantics).

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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