Re: [Qemu-devel] [RFC][PATCH 09/15] introduce a new monitor command 'dump' to dump guest's memory

[Wen Congyang <wency@cn.fujitsu.com>]

At 01/20/2012 12:32 AM, Eric Blake Wrote:
> On 01/18/2012 08:07 PM, Wen Congyang wrote:
>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
>> ---
>>  Makefile.target  |    8 +-
>>  dump.c           |  590 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  dump.h           |    3 +
>>  hmp-commands.hx  |   16 ++
>>  hmp.c            |    9 +
>>  hmp.h            |    1 +
>>  monitor.c        |    3 +
>>  qapi-schema.json |   13 ++
>>  qmp-commands.hx  |   26 +++
>>  9 files changed, 665 insertions(+), 4 deletions(-)
>>  create mode 100644 dump.c
>>
> 
>> +void qmp_dump(const char *file, Error **errp)
>> +{
>> +    const char *p;
>> +    int fd = -1;
>> +    DumpState *s;
>> +
>> +#if !defined(WIN32)
>> +    if (strstart(file, "fd:", &p)) {
>> +        fd = qemu_get_fd(p);
>> +        if (fd == -1) {
>> +            error_set(errp, QERR_FD_NOT_FOUND, p);
>> +            return;
>> +        }
>> +    }
>> +#endif
> 
> Thanks for implementing fd support off the bat.
> 
>> +
>> +    if  (strstart(file, "file:", &p)) {
>> +        fd = open(p, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY);
> 
> Use of O_CREAT requires that you pass a third argument to open()
> specifying the mode_t to use.

Yes, I forgot it, and will fix it.

> 
>> +++ b/hmp-commands.hx
>> @@ -828,6 +828,22 @@ new parameters (if specified) once the vm migration finished successfully.
>>  ETEXI
>>  
>>      {
>> +        .name       = "dump",
>> +        .args_type  = "file:s",
>> +        .params     = "file",
>> +        .help       = "dump to file",
>> +        .user_print = monitor_user_noop,
>> +        .mhandler.cmd = hmp_dump,
>> +    },
> 
> What if I want to dump only a fraction of the memory?  I think you need
> optional start and length parameters, to limit how much memory to be
> dumped, rather than forcing me to dump all memory at once.
> 

It is OK to support it, but I do not know why do you want it?

The purpose of this command is dumping the memory when the guest is paniced.
And then we can use crash/gdb(or other application) to investigate why the guest
is paniced. So we should dump the whole memory.

Thanks
Wen Congyang