Re: [patch part-III V2 05/23] x86/entry/32: Provide macro to emit IDT entry stubs

[Thomas Gleixner]

Brian Gerst <brgerst@xxxxxxxxx> writes:
> On Sun, Mar 8, 2020 at 7:24 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> +#ifdef CONFIG_X86_INVD_BUG
>> +.macro idtentry_push_func vector cfunc
>> +       .if \vector == X86_TRAP_XF
>> +               /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
>> +               ALTERNATIVE "pushl      $do_general_protection",        \
>> +                           "pushl      $do_simd_coprocessor_error",    \
>> +                           X86_FEATURE_XMM
>> +       .else
>> +               pushl $\cfunc
>> +       .endif
>> +.endm
>> +#else
>> +.macro idtentry_push_func vector cfunc
>> +       pushl $\cfunc
>> +.endm
>> +#endif
>
> IMHO it would be better to push this to the C code and not make the
> asm more complicated.  Something like:
>
> dotraplinkage void
> do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
> {
> #ifdef CONFIG_X86_INVD_BUG
>         /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
>         if (!static_cpu_has(X86_FEATURE_XMM)) {
>                 do_general_protection(regs, error_code);
>                 return;
>         }
> #endif
>         RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
>         math_error(regs, error_code, X86_TRAP_XF);
> }

That's too obvious :)

Thanks for catching that!

       tglx