Re: [Qemu-devel] [PATCH v2] stop using stdio for monitor/serial/etc with -daemonize

[Anthony Liguori <anthony@codemonkey.ws>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On 26 September 2012 09:17, Michael Tokarev <mjt@tls.msk.ru> wrote:
>> On 26.09.2012 12:00, Peter Maydell wrote:
>>
>>>> I know lots of people use -nographic -daemonize to run headless
>>>> guests in background (like, for example, a router).  I guess it
>>>> come way before -vga option has been introduced, but at least I
>>>> know about -vga (but not about -vga none).  For one, I never saw
>>>> -display before.  And it looks like -nographic is a synonym for
>>>> -display none, and -curses is a synonym for -display curses.
>>
>> I mean, -nographic is about the same as -vga none -display none.
>
> ...except that it *also* messes around with where the serial output
> goes and with the parallel port and maybe something else.
>
>> What is equivalent of -nographic in terms of -vga/-display/-...?
>> From the code it is something like
>>
>>  -vga none -display none -serial mon:stdio -parallel null
>
> It's something like that. It would be nice to implement -nographic
> as "this is an alias for ...." but IIRC it isn't quite doable.
> (maybe I misremember)
>
>> (this is the code I tried to patch).
>>
>> Note: this, compbined with -daemonize, also has the same issue,
>> namely, the tty is left in a bad state after qemu process backgrounded,
>> and for the very same reason: -serial stdio switches the try into
>> raw mode.  So this should be fixed too -- somehow, either by forbidding
>> this combination completely or by silently substituting stdio for
>> -serial with null.  But it will be done in a subsequent patch.
>>
>> Note also: by forbidding -nographic -daemonize, we'll break lots of
>> existing setups too, and I still don't see why this combination is
>> bad, I already demonstrated that it can be made to work in a more
>> or less reasonable/expected way.
>
> Because you've asked both "put me into the background" and "please
> send stuff to stdio". Admittedly you've probably done that because
> you didn't really understand that '-nographic' doesn't mean
> '-display none', but you've still asked for a nonsensical combination.

This is a good example of where we need improved documentation but I
agree 100% with Peter.

Regards,

Anthony Liguori

>
> -- PMM