Re: [PATCH] LoongArch: Make -mstrict-align be configurable

[Huacai Chen]

Hi, David,

On Thu, Feb 2, 2023 at 5:01 PM David Laight <David.Laight@xxxxxxxxxx> wrote:
>
> From: Huacai Chen
> > Sent: 02 February 2023 08:43
> >
> > Introduce Kconfig option ARCH_STRICT_ALIGN to make -mstrict-align be
> > configurable.
> >
> > Not all LoongArch cores support h/w unaligned access, we can use the
> > -mstrict-align build parameter to prevent unaligned accesses.
> >
> > This option is disabled by default to optimise for performance, but you
> > can enabled it manually if you want to run kernel on systems without h/w
> > unaligned access support.
>
> Should there be an associated run-time check during kernel initialisation
> that a kernel compiled without -mstrict-align isn't being run on hardware
> that doesn't support unaligned accesses.
>
> It can be quite a while before you get a compiler-generated misaligned accesses.
If we don't use -mstrict-align, the kernel cannot be run on hardware
that doesn't support unaligned accesses, so I think the run-time check
is useless, and it has no chance to run the checking.

>
> Also isn't there a HAVE_EFFICIENT_MISALIGNED_ACCESS define that would
> also need to be set correctly??
Yes, HAVE_EFFICIENT_MISALIGNED_ACCESS should be kept consistency with
ARCH_STRICT_ALIGN, thank you.

Huacai
>
>         David
>
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