Re: [Qemu-devel] [PATCH] Allow to leave type on default in -machine

[Anthony Liguori <aliguori@us.ibm.com>]

On 07/25/2011 11:11 AM, Jan Kiszka wrote:
> On 2011-07-25 13:48, Jan Kiszka wrote:
>> On 2011-07-25 13:39, Markus Armbruster wrote:
>>> Jan Kiszka<jan.kiszka@siemens.com>  writes:
>>>
>>>> On 2011-07-25 12:45, Richard W.M. Jones wrote:
>>>>> On Mon, Jul 25, 2011 at 12:33:01PM +0200, Jan Kiszka wrote:
>>>>>> On 2011-07-25 11:41, Richard W.M. Jones wrote:
>>>>>>> On Sat, Jul 23, 2011 at 12:38:37PM +0200, Jan Kiszka wrote:
>>>>>>>> From: Jan Kiszka<jan.kiszka@siemens.com>
>>>>>>>>
>>>>>>>> -machine somehow suggests that it selects the machine, but it doesn't.
>>>>>>>> Fix that before this command is set in stone.
>>>>>>>>
>>>>>>>> Actually, -machine should supersede -M and allow to introduce arbitrary
>>>>>>>> per-machine options to the command line. That will change the internal
>>>>>>>> realization again, but we will be able to keep the user interface
>>>>>>>> stable.
>>>>>>>
>>>>>>> This breaks libguestfs which was doing:
>>>>>>>
>>>>>>>    qemu -machine accel=kvm:tcg ...
>>>>>>>
>>>>>>> We are not passing any -M option at all.  We don't particularly care
>>>>>>> about the machine type since we're not that performance sensitive and
>>>>>>> we don't need to serialize the machine state.
>>>>>>>
>>>>>>> I have checked, and this works:
>>>>>>>
>>>>>>>    qemu -machine pc,accel=kvm:tcg ...
>>>>>>>
>>>>>>> "pc" is the default, right?  What about for other architectures?
>>>>>>
>>>>>> Yes, pc is the right default. Other arch have other defaults.
>>>>>
>>>>> So what you're saying is we have to parse qemu -machine \? output by
>>>>> looking for the string '(default)'?  eg:
>>>>>
>>>>> $ ./arm-softmmu/qemu-system-arm -machine \?|fgrep '(default)'
>>>>> integratorcp ARM Integrator/CP (ARM926EJ-S) (default)
>>>>>
>>>>> $ ./i386-softmmu/qemu -machine \?|fgrep '(default)'
>>>>> pc-0.14    Standard PC (default)
>>>>
>>>> I understand, this is clumsy. Will see if we can do better.
>>>
>>> Is there a technical reason why type isn't optional with -machine?
>>>
>>> [...]
>>
>> Maybe it's just the
>>
>> assert(!permit_abbrev || list->implied_opt_name);
>>
>> in qemu_opts_parse, but I haven't looked at all details (and all other
>> users) yet.
>
> I was incorrectly pointing the core, the problem is solvable at the
> level where we parse -machine:
>
> -------8<--------
>
> This allows to specify -machine options without setting an explicit
> machine type. We will pick the default machine in this case. Requesting
> the list of available machines is still possible via '-machine ?' e.g.
>
> Signed-off-by: Jan Kiszka<jan.kiszka@siemens.com>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
>   vl.c |    5 ++++-
>   1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 8256504..5e53ddc 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2720,7 +2720,10 @@ int main(int argc, char **argv, char **envp)
>                       fprintf(stderr, "parse error: %s\n", optarg);
>                       exit(1);
>                   }
> -                machine = machine_parse(qemu_opt_get(opts, "type"));
> +                optarg = qemu_opt_get(opts, "type");
> +                if (optarg) {
> +                    machine = machine_parse(optarg);
> +                }
>                   break;
>               case QEMU_OPTION_usb:
>                   usb_enabled = 1;