Re: [Qemu-devel] [RFC PATCH] hw/core: expand description of null-machine

[Thomas Huth]

On 25.04.2018 17:33, Alex Bennée wrote:
> People following old instructions for QEMU get the message "No machine
> specified, and there is no default" and run -machine help to pick a
> new machine. Lay people might consider the null-machine to be such a
> basic starting point but they won't get far. This leads to confusion,
> see https://bugs.launchpad.net/qemu/+bug/1766896 as an example.
> 
> I'm open to better words - I figured "THIS PROBABLY ISN'T WHAT YOU
> WANT" seemed less helpful though.
> 
> Signed-off-by: Alex Bennée <address@hidden>
> ---
>  hw/core/null-machine.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/core/null-machine.c b/hw/core/null-machine.c
> index cde4d3eb57..72f0815045 100644
> --- a/hw/core/null-machine.c
> +++ b/hw/core/null-machine.c
> @@ -50,7 +50,7 @@ static void machine_none_init(MachineState *mch)
>  
>  static void machine_none_machine_init(MachineClass *mc)
>  {
> -    mc->desc = "empty machine";
> +    mc->desc = "empty machine (for probing/QMP)";

Actually, with certain CPUs, you can really use the "none" machine as a
pure instruction set testing system. For example, on m68k, there used to
be an explicit "dummy" machine for this job, and we removed it in favour
of the "none" machine:

https://git.qemu.org/?p=qemu.git;a=commitdiff;h=22f2dbe7eaf3e12e38c9c210

So I'd rather not add such wording. We should rather fix those segfaults
instead (QEMU should never segfault - in case a device can not be used
with the "none" machine, there rather should be an error message instead).

 Thomas