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Re: [Qemu-devel] Any approach to log the file read/write (I/O data flow)

From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] Any approach to log the file read/write (I/O data flow) like the "-d in_asm" option?
Date: Thu, 7 Jun 2012 16:02:10 +0100

On Thu, Jun 7, 2012 at 4:24 AM, 陳韋任 (Wei-Ren Chen)
<address@hidden> wrote:
> On Wed, Jun 06, 2012 at 11:23:37AM +0100, Stefan Hajnoczi wrote:
>> On Sun, Jun 3, 2012 at 9:50 PM, Yue Chen <address@hidden> wrote:
>> > I'm doing something like a simple and lightweight REPLAY program out of
>> > QEMU, only including CPU, MEMORY, and DISK. I'm implementing it with a
>> > shadow CPU (register state), shadow memory(from?"pmemsave") and shadow
>> > ".img" file (disk).
>> Why doesn't the "savevm" command provide the snapshotting you need?
>> It sounds like you're trying to do VM snapshots yourself.
>  Does `savevm` and reply do the same thing? :)

No.  'savevm' and 'loadvm' are purely for saving and restoring a
snapshot of the VM disk, RAM, and devices.

Replay is something that could be built on top of that snapshotting
functionality, and I think it's something along the lines of why
savevm/loadvm were added and why qcow2 has internal snapshots (before
my time but I think Fabrice was working on something like replay or
reversible debugging).  But replay is really hard for a system that
interacts with the outside world (e.g. internet).


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