[libvirt] [PATCH 0/2] use qemu's dump-guest-meory when vm uses host device

[Wen Congyang]

At 04/02/2012 10:50 PM, Eric Blake Wrote:
> On 04/01/2012 10:01 PM, Wen Congyang wrote:
>> Currently, we use migrate to dump guest's memory. There is one
>> restriction in migrate command: the device's status should be
>> stored in qemu because the device's status should be passed to
>> target machine.
>>
>> If we passthrough a host device to guest, the device's status
>> is stored in the real device. So migrate command will fail.
>>
>> We usually use dump when guest is panicked. So there is no need
>> to store device's status in the vmcore.
>>
>> qemu will have a new monitor command dump-guest-memory to dump
>> guest memory, but it doesn't support async now(it will support
>> later when the common async API is implemented).
> 
> I've seen conversation on this patch on qemu-devel, but is it actually
> committed yet, or still pending there?  This is late enough that it
> should wait until after 0.9.11 to actually be applied, so I haven't
> quite reviewed it yet.

The patch on qemu-devel is still pending there. QMP maitainer Luiz
has acked it, but he waits an ack from Jan and/or Anthony.

> 
>>
>> So I use dump-guest-memory only when the guest uses host device
>> in this patchset.
>>
>> Wen Congyang (2):
>>   qemu: implement qemu's dump-guest-memory
>>   qemu: try to use qemu's dump-guest-meory when vm uses host device
>>
>>  src/qemu/qemu_domain.c       |    1 +
>>  src/qemu/qemu_domain.h       |    1 +
>>  src/qemu/qemu_driver.c       |   42 ++++++++++++++++++++-
>>  src/qemu/qemu_monitor.c      |   32 ++++++++++++++++
>>  src/qemu/qemu_monitor.h      |   13 +++++++
>>  src/qemu/qemu_monitor_json.c |   42 +++++++++++++++++++++
>>  src/qemu/qemu_monitor_json.h |    7 ++++
>>  src/qemu/qemu_monitor_text.c |   83 ++++++++++++++++++++++++++++++++++++++++++
> 
> Why are we bothering with a text implementation?  We know that the
> feature is only present if you have qemu 1.1 or later (assuming that
> qemu-devel did apply your series adding the monitor command), and
> therefore we know that we have QMP, so we should only implement this for
> JSON and not bother with the text monitor.
> 

In most cases, the libvirt is built with json. But if the libvirt is built
without json, we will use text monitor.