RE: [PATCH v7 15/35] Hexagon (target/hexagon/arch.[ch]) utility functions

[Taylor Simpson]

> -----Original Message-----
> From: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com> On
> Behalf Of Philippe Mathieu-Daudé
> Sent: Monday, January 25, 2021 10:30 AM
> To: Taylor Simpson <tsimpson@quicinc.com>; qemu-devel@nongnu.org
> Cc: ale@rev.ng; alex.bennee@linaro.org; richard.henderson@linaro.org;
> laurent@vivier.eu; Brian Cain <bcain@quicinc.com>
> Subject: Re: [PATCH v7 15/35] Hexagon (target/hexagon/arch.[ch]) utility
> functions
>
> >>> diff --git a/target/hexagon/arch.c b/target/hexagon/arch.c
> >>> new file mode 100644
> >>> index 0000000..c59cad5
> >>> --- /dev/null
> >>> +++ b/target/hexagon/arch.c
> >> ...
> >>
> >>> +#define RAISE_FP_EXCEPTION \
> >>> +    do {} while (0)            /* Not modelled in qemu user mode */
> >>
> >> I don't understand why... Can you explain please?
> >
> > Our Linux kernel only sets the relevant bits in USR (user status register).
> The exception isn't raised to user mode.
>
> Hmm while you introduce the linux-user implementation of your port,
> this file is not restricted to user mode. Thinking about avoiding
> head aches to someone wanting to add system mode emulation (or a
> BSD port??), maybe your helpers should consider that.
> Maybe some cheap #ifdef'ry CONFIG_USER_ONLY with a comment
> explaining
> why there is nothing to do in user mode, and g_assert_not_reached()
> else. Not sure, just wondering...

Sorry, I misunderstood the question.  You are correct.  It's a placeholder for 
future work to support system mode.  I'll add the #ifdef and some comments to 
explain.

Thanks,
Taylor