HMP: support specifying dump format for dump-guest-memory

Dumping guest memory is available to specify the dump format now. This patch
adds options '-z|-l|-s' to HMP command dump-guest-memory to specify dumping in
kdump-compression format, with zlib/lzo/snappy compression. And without these
options ELF format will be used.

The discussion about this feature is here:

http://lists.nongnu.org/archive/html/qemu-devel/2014-03/msg04235.html

Signed-off-by: Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> (on s390x/kvm)
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index d79cb97..8971f1b 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1000,10 +1000,13 @@
 
     {
         .name       = "dump-guest-memory",
-        .args_type  = "paging:-p,filename:F,begin:i?,length:i?",
-        .params     = "[-p] filename [begin length]",
+        .args_type  = "paging:-p,zlib:-z,lzo:-l,snappy:-s,filename:F,begin:i?,length:i?",
+        .params     = "[-p] [-z|-l|-s] filename [begin length]",
         .help       = "dump guest memory into file 'filename'.\n\t\t\t"
                       "-p: do paging to get guest's memory mapping.\n\t\t\t"
+                      "-z: dump in kdump-compressed format, with zlib compression.\n\t\t\t"
+                      "-l: dump in kdump-compressed format, with lzo compression.\n\t\t\t"
+                      "-s: dump in kdump-compressed format, with snappy compression.\n\t\t\t"
                       "begin: the starting physical address.\n\t\t\t"
                       "length: the memory size, in bytes.",
         .mhandler.cmd = hmp_dump_guest_memory,
@@ -1012,10 +1015,14 @@
 
 STEXI
 @item dump-guest-memory [-p] @var{filename} @var{begin} @var{length}
+@item dump-guest-memory [-z|-l|-s] @var{filename}
 @findex dump-guest-memory
 Dump guest memory to @var{protocol}. The file can be processed with crash or
-gdb.
+gdb. Without -z|-l|-s, the dump format is ELF.
         -p: do paging to get guest's memory mapping.
+        -z: dump in kdump-compressed format, with zlib compression.
+        -l: dump in kdump-compressed format, with lzo compression.
+        -s: dump in kdump-compressed format, with snappy compression.
   filename: dump file name.
      begin: the starting physical address. It's optional, and should be
             specified together with length.