Hi, Arnd, On Thu, Feb 2, 2023 at 5:47 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Thu, Feb 2, 2023, at 09:42, Huacai Chen wrote: > > 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. > > > > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx> > > This feels like it's a way too low-level option, I would not expect > users to be able to answer this correctly. > > What I would do instead is to have Kconfig options for specific > CPU implementations and derive the alignment requirements from > that. You mean provide something like CONFIG_CPU_XXXX as MIPS do? That seems not a good idea, too. If there are more than 3 CONFIG_CPU_XXXX, the complexity is more than CONFIG_ARCH_STRICT_ALIGN. Then users are also unable to do a correct selection. On the other hand, we can add more words under CONFIG_ARCH_STRICT_ALIGN to describe which processors support hardware unaligned accesses. Huacai > > > +config ARCH_STRICT_ALIGN > > + bool "Enable -mstrict-align to prevent unaligned accesses" > > + help > > + Not all LoongArch cores support h/w unaligned access, we can use > > + -mstrict-align build parameter to prevent unaligned accesses. > > + > > + This is disabled by default to optimise for performance, you can > > + enabled it manually if you want to run kernel on systems without > > + h/w unaligned access support. > > + > > > There is already a global CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > option, I think you should use that one instead of adding another > one. Setting HAVE_EFFICIENT_UNALIGNED_ACCESS for CPUs that can > do unaligned access will enable some important optimizations in > the network stack and a few other places. > > Arnd
