Re: [Qemu-devel] [PATCH 4/4] HMP: Introduce console command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 30 Oct 2012 18:22:34 +0800
Lei Li <lilei@linux.vnet.ibm.com> wrote:

> On 10/29/2012 09:26 PM, Luiz Capitulino wrote:
> > On Mon, 29 Oct 2012 12:18:03 +0800
> > Lei Li <lilei@linux.vnet.ibm.com> wrote:
> >
> >> On 10/27/2012 01:43 AM, Luiz Capitulino wrote:
> >>> On Fri, 26 Oct 2012 19:21:52 +0800
> >>> Lei Li <lilei@linux.vnet.ibm.com> wrote:
> >>>
> >>>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> >>> I still don't understand how this command, in its current form, is
> >>> different from memchar-write.
> >>>
> >>> One more comment below.
> >> Hi Luiz,
> >>
> >> Yes, I have replied to it in patch series v4. You can look at it
> >> as link below:
> >>
> >> https://lists.gnu.org/archive/html/qemu-devel/2012-10/msg04568.html
> > Unfortunately your answer doesn't answer my (honest) question. Can you actually
> > show me how the console command is better than the memchar-write one? Maybe
> > I'm missing something obvious...
> 
> As the example I post in the link, I think the main benefit for console command
> is that it's more friendly.
> 
> A simple example, when we try to input "hello world" to this char device,
> the memchar_write command would like this:
> 
> (qemu) memchar_write foo "hello world"
> 
> We need to add quotation marks for the string due to the monitor behaver.(Would
> treat as another argument for the string which has space in it.)
> 
> The console command can avoid this like:
> 
> (qemu) console foo
> foo: hello world
> \r / ^]
> (qemu)
> 
> It drops you into an interactive mode where it's like your at the serial console
> and \r or ctrl-] escape sequences takes you back to the monitor suggested by Anthony.

I really think this is wrong. In its current form, this command is
memchar_write with a prompt.

My understanding of a console command is that you attach to the serial port,
see stuff being written by the guest and is able to also write stuff.

> I hope this can answer your question. :)
> 
> >>>> ---
> >>>>    hmp-commands.hx |   25 +++++++++++++++++++++++++
> >>>>    hmp.c           |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >>>>    hmp.h           |    1 +
> >>>>    monitor.c       |   15 +++++++++++++++
> >>>>    monitor.h       |    3 +++
> >>>>    5 files changed, 96 insertions(+), 0 deletions(-)
> >>>>
> >>>> diff --git a/hmp-commands.hx b/hmp-commands.hx
> >>>> index df294eb..7cba42c 100644
> >>>> --- a/hmp-commands.hx
> >>>> +++ b/hmp-commands.hx
> >>>> @@ -861,6 +861,31 @@ if the requested size is larger than it.
> >>>>    ETEXI
> >>>>    
> >>>>        {
> >>>> +        .name       = "console",
> >>>> +        .args_type  = "chardev:s",
> >>>> +        .params     = "chardev",
> >>>> +        .help       = "Connect to the serial console from within the"
> >>>> +                      "monitor, allow to write data to memchardev"
> >>>> +                      "'chardev'. Exit from the console and return back"
> >>>> +                      "to monitor by typing 'ctrl-]'",
> >>>> +        .mhandler.cmd = hmp_console,
> >>>> +    },
> >>>> +
> >>>> +STEXI
> >>>> +@item console @var{device}
> >>>> +@findex console
> >>>> +
> >>>> +Connect to the serial console from within the monitor, allow to write data
> >>>> +to memchardev @var{chardev}. Exit from the console and return back to
> >>>> +monitor by typing 'ctrl-]'.
> >>>> +@example
> >>>> +(qemu) console foo
> >>>> +foo: data string...
> >>>> +@end example
> >>>> +
> >>>> +ETEXI
> >>>> +
> >>>> +    {
> >>>>            .name       = "migrate",
> >>>>            .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
> >>>>            .params     = "[-d] [-b] [-i] uri",
> >>>> diff --git a/hmp.c b/hmp.c
> >>>> index ef85736..d716410 100644
> >>>> --- a/hmp.c
> >>>> +++ b/hmp.c
> >>>> @@ -1255,3 +1255,55 @@ void hmp_screen_dump(Monitor *mon, const QDict *qdict)
> >>>>        qmp_screendump(filename, &err);
> >>>>        hmp_handle_error(mon, &err);
> >>>>    }
> >>>> +
> >>>> +enum escape_char
> >>>> +{
> >>>> +    ESCAPE_CHAR_CTRL_GS = 0x1d  /* ctrl-] used for escape */
> >>>> +};
> >>>> +
> >>>> +static void hmp_read_console(Monitor *mon, const char *data,
> >>>> +                             void *opaque)
> >>>> +{
> >>>> +    CharDriverState *chr = opaque;
> >>>> +    uint32_t size = strlen(data);
> >>>> +    enum DataFormat format = DATA_FORMAT_UTF8;
> >>>> +    enum escape_char console_escape = ESCAPE_CHAR_CTRL_GS;
> >>>> +
> >>>> +    Error *err = NULL;
> >>>> +
> >>>> +    if (*data == console_escape) {
> >>>> +        monitor_resume(mon);
> >>>> +        return;
> >>>> +    }
> >>>> +
> >>>> +    qmp_memchar_write(chr->label, size, data, 0, format, &err);
> >>>> +
> >>>> +    if (err) {
> >>>> +        monitor_printf(mon, "%s\n", error_get_pretty(err));
> >>>> +        error_free(err);
> >>>> +        return;
> >>>> +    }
> >>>> +
> >>>> +    monitor_read_command(mon, 1);
> >>>> +}
> >>>> +
> >>>> +void hmp_console(Monitor *mon, const QDict *qdict)
> >>>> +{
> >>>> +    const char *device = qdict_get_str(qdict, "chardev");
> >>>> +    CharDriverState *chr;
> >>>> +    Error *err = NULL;
> >>>> +
> >>>> +    chr = qemu_chr_find(device);
> >>>> +
> >>>> +    if (!chr) {
> >>>> +        error_set(&err, QERR_DEVICE_NOT_FOUND, device);
> >>>> +        goto out;
> >>>> +    }
> >>> As I said before, I don't why chr is needed. It seems to me that passing
> >>> 'device' down is enough.
> >>>
> >>>> +
> >>>> +    if (monitor_read_console(mon, device, hmp_read_console, chr) < 0) {
> >>>> +        monitor_printf(mon, "Connect to console %s failed\n", device);
> >>>> +    }
> >>>> +
> >>>> +out:
> >>>> +    hmp_handle_error(mon, &err);
> >>>> +}
> >>>> diff --git a/hmp.h b/hmp.h
> >>>> index a5a0cfe..5b54a79 100644
> >>>> --- a/hmp.h
> >>>> +++ b/hmp.h
> >>>> @@ -77,5 +77,6 @@ void hmp_getfd(Monitor *mon, const QDict *qdict);
> >>>>    void hmp_closefd(Monitor *mon, const QDict *qdict);
> >>>>    void hmp_send_key(Monitor *mon, const QDict *qdict);
> >>>>    void hmp_screen_dump(Monitor *mon, const QDict *qdict);
> >>>> +void hmp_console(Monitor *mon, const QDict *qdict);
> >>>>    
> >>>>    #endif
> >>>> diff --git a/monitor.c b/monitor.c
> >>>> index d17ae2d..7e90115 100644
> >>>> --- a/monitor.c
> >>>> +++ b/monitor.c
> >>>> @@ -256,6 +256,21 @@ int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
> >>>>        }
> >>>>    }
> >>>>    
> >>>> +int monitor_read_console(Monitor *mon, const char *device,
> >>>> +                         ReadLineFunc *readline_func, void *opaque)
> >>>> +{
> >>>> +    char prompt[60];
> >>>> +
> >>>> +    if (!mon->rs) {
> >>>> +        return -1;
> >>>> +    }
> >>>> +
> >>>> +    snprintf(prompt, sizeof(prompt), "%s: ", device);
> >>>> +    readline_start(mon->rs, prompt, 0, readline_func, opaque);
> >>>> +
> >>>> +    return 0;
> >>>> +}
> >>>> +
> >>>>    void monitor_flush(Monitor *mon)
> >>>>    {
> >>>>        if (mon && mon->outbuf_index != 0 && !mon->mux_out) {
> >>>> diff --git a/monitor.h b/monitor.h
> >>>> index b6e7d95..735bd1b 100644
> >>>> --- a/monitor.h
> >>>> +++ b/monitor.h
> >>>> @@ -86,6 +86,9 @@ ReadLineState *monitor_get_rs(Monitor *mon);
> >>>>    int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
> >>>>                              void *opaque);
> >>>>    
> >>>> +int monitor_read_console(Monitor *mon, const char *device,
> >>>> +                         ReadLineFunc *readline_func, void *opaque);
> >>>> +
> >>>>    int qmp_qom_set(Monitor *mon, const QDict *qdict, QObject **ret);
> >>>>    
> >>>>    int qmp_qom_get(Monitor *mon, const QDict *qdict, QObject **ret);
> >>
> 
>