Re: [tip: x86/fpu] x86/fpu: Use XSAVE{,OPT,C,S} and XRSTOR{,S} mnemonics in xstate.h

[Borislav Petkov]

On Mon, Mar 17, 2025 at 11:28:58AM +0100, Uros Bizjak wrote:
> > > @@ -114,10 +113,10 @@ static inline int update_pkru_in_sigframe(struct xregs_state __user *buf, u64 ma
> > >  #define XSTATE_OP(op, st, lmask, hmask, err)                         \
> > >       asm volatile("1:" op "\n\t"                                     \
> > >                    "xor %[err], %[err]\n"                             \
> > > -                  "2:\n\t"                                           \
> > > +                  "2:\n"                                             \
> > >                    _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_FAULT_MCE_SAFE)  \
> > >                    : [err] "=a" (err)                                 \
> > > -                  : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)    \
> > > +                  : [xa] "m" (*(st)), "a" (lmask), "d" (hmask)       \
> >
> > This [xa] needs documenting in the comment above this.
> >
> > What does "xa" even mean?
> 
> xsave area.

That's struct xregs_state in kernel nomenclature.

And the macro's argument is called "st".

And when it says [xa] there, one wonders where that "xa" comes from. So please
add a comment above the macro explaining that.

And you can redo the whole patch - it is the topmost one in tip:x86/fpu and
can simply be replaced.

Thx.

-- 
Regards/Gruss,
    Boris.

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