Re: [PATCH v5 08/11] target/loongarch: Reject la64-only instructions in la32 mode

[gaosong]

在 2023/8/9 下午11:03, Richard Henderson 写道:
> On 8/9/23 01:26, Jiajie Chen wrote:
> > LoongArch64-only instructions are marked with regard to the instruction
> > manual Table 2. LSX instructions are not marked for now for lack of
> > public manual.
>
> I would expect LSX not to be affected by CPUCFG.1.ARCH, but only by 
> CPUCFG.2.LSX.
>
> Note that there appears to be a bug with respect to LSX, in that 
> CPUCFG.2.LSX is not checked.  The manual is not clear, but I would 
> expect CPUCFG.2.LSX == 0 to trigger an illegal instruction exception 
> before the check for EUEN.SXE == 0 to trigger an instruction disabl > exception.  Also, are bit in EUEN allowed to be set to non-zero values
> when the corresponding expansion is not present?
No, the kernel always checks for corresponding extensions when setting EUEN.

See enable_fpu/lsx/lasx at

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/include/asm/fpu.h?h=v6.5-rc5

And, I will send a patch to Check CPUCFG.2.LSX, Thanks for you suggestion.

Thanks.
Song Gao.