[Qemu-devel] Re: [RFC][PATCH v1 08/12] qemu-char: add qmp_proxy chardev

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On 03/25/2011 04:29 PM, Anthony Liguori wrote:
> On 03/25/2011 02:47 PM, Michael Roth wrote:
>> This allows qemu to be started with guest agent support via:
>>
>> qemu -chardev qmp_proxy,path=<optional>,id=qmp_proxy \
>> -device ...,chardev=qmp_proxy
>>
>> It is essentially a wrapper for -chardev socket, which takes the extra
>> step of setting required defaults and initializing the qmp proxy by
>> passing the path argument along.
>>
>> Not sure if this is the most elegant approach, but in terms of the
>> command-line invocation it seems to be the most consistent way to do
>> it.
>>
>> Signed-off-by: Michael Roth<mdroth@linux.vnet.ibm.com>
>> ---
>> qemu-char.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>> 1 files changed, 46 insertions(+), 0 deletions(-)
>>
>> diff --git a/qemu-char.c b/qemu-char.c
>> index d301925..6ff7698 100644
>> --- a/qemu-char.c
>> +++ b/qemu-char.c
>> @@ -2275,6 +2275,51 @@ static CharDriverState
>> *qemu_chr_open_socket(QemuOpts *opts)
>> return NULL;
>> }
>>
>> +#include "qmp-proxy-core.h"
>> +
>> +extern QmpProxy *qmp_proxy_default;
>> +
>> +static CharDriverState *qemu_chr_open_qmp_proxy(QemuOpts *opts)
>> +{
>> + CharDriverState *chr;
>> + QmpProxy *p;
>> + const char *path;
>> +
>> + /* revert to/enforce default socket chardev options for qmp proxy */
>> + path = qemu_opt_get(opts, "path");
>> + if (path == NULL) {
>> + path = QMP_PROXY_PATH_DEFAULT;
>> + qemu_opt_set_qerr(opts, "path", path);
>> + }
>> + /* required options for qmp proxy */
>> + qemu_opt_set_qerr(opts, "server", "on");
>> + qemu_opt_set_qerr(opts, "wait", "off");
>> + qemu_opt_set_qerr(opts, "telnet", "off");
>
> Why are these options required?

The qmp_proxy_new() constructor expects a path to a socket it can 
connect() to. Not sure about telnet, but the other options are required 
for this. Well...server=on at least, wait=off needs to be set as well 
because that's the only way to have the socket chardev set the listening 
socket to non-block, since qmp_proxy_new() calls connect() on it before 
we return to the main I/O loop.

Although, we probably shouldn't just silently switch out explicitly set 
options; an error would probably be more appropriate here.

>
> Regards,
>
> Anthony Liguori
>