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Re: [libvirt] [PATCH 0/2 v3 use qemu's dump-guest-meory when vm uses host device



At 04/19/2012 04:38 PM, Daniel P. Berrange Wrote:
> On Thu, Apr 19, 2012 at 09:03:16AM +0800, 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).
>>
>> So I use dump-guest-memory only when the guest uses host device
>> in this patchset.
> 
> Hmm, doesn't the new command generate dump files in a totally
> different format to the existing command ?  If so I don't
> think it is nice behaviour to silently switch between 2 different
> dump formats depending on the XML config.  I think we'd want some
> kind of flag to specify what format is desired.

Agree with it. But the new command is not a async command, and it
will block the other operation. So I only use it when the vm uses
host device(migrate command will fail in this case).

The new command will be converted to async command later(after
async API is implemented). I think we can allow the user specify
the format when the new command is async command.

Thanks
Wen Congyang

> 
> Daniel


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