Re: [Qemu-devel] [PATCH] armv7m: optional -kernel if -gdb present

[Peter Maydell]

On 20 November 2014 13:09, Liviu Ionescu <address@hidden> wrote:
>
> On 20 Nov 2014, at 14:50, Peter Maydell <address@hidden> wrote:
>
>> Same thing as if you start a hardware board with nothing loaded
>> into the flash. (Probably this means "go into an infinite loop
>> of taking exceptions".)
>
> hmmm... and you consider this behaviour to meet the user-friendly 
> requirements?
>
> I tried it, and the program simply hangs, without any stdout/stderr messages.

Yes. That's what hardware does in that situation.

I don't think that whether or not a debugger has been connected
should change our behaviour. (And even with your patch, if you
connect a debugger and just hit its 'run' button without loading
an image then we'll do the same exception-loop.)

> if you find this behaviour acceptable for unix users, ok, you don't
> have to update the other profiles, but for most cortex-m users it is
> confusing, and user-friendliness is not only appreciated, but required.

I agree it's not very user friendly. But I don't like inconsistency
between our behaviour for different boards either. (And for some
boards we're going to have a bios or other firmware which will
run if you don't specify -kernel.)

In general I think many of the concerns you're raising here
are real problems, and our user-friendliness is indeed poor
in a lot of places. However the solutions you're proposing
are often specific to M-profile ARM, whereas I have to consider
the whole project and would prefer solutions which clean
up and deal with an issue for all boards and all CPUs.
That's obviously harder than a more local and restricted
fix, but the benefit is greater.

thanks
-- PMM