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

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Message-ID: <CAFULd4b-sZucEtvx19==5wcOfOCzj5fuZ2SHS7ZMboZQXdVycg@mail.gmail.com>
Date: Mon, 17 Mar 2025 11:28:58 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org, 
	Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>, Brian Gerst <brgerst@...il.com>, 
	"H. Peter Anvin" <hpa@...or.com>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org
Subject: Re: [tip: x86/fpu] x86/fpu: Use XSAVE{,OPT,C,S} and XRSTOR{,S}
 mnemonics in xstate.h

On Mon, Mar 17, 2025 at 11:14 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Thu, Mar 13, 2025 at 05:50:34PM -0000, tip-bot2 for Uros Bizjak wrote:
> > The following commit has been merged into the x86/fpu branch of tip:
> >
> > Commit-ID:     2883b4c2169a435488f7845e1b6fdc6f3438c7c6
> > Gitweb:        https://git.kernel.org/tip/2883b4c2169a435488f7845e1b6fdc6f3438c7c6
> > Author:        Uros Bizjak <ubizjak@...il.com>
> > AuthorDate:    Thu, 13 Mar 2025 14:02:27 +01:00
> > Committer:     Ingo Molnar <mingo@...nel.org>
> > CommitterDate: Thu, 13 Mar 2025 18:36:52 +01:00
> >
> > x86/fpu: Use XSAVE{,OPT,C,S} and XRSTOR{,S} mnemonics in xstate.h
> >
> > Current minimum required version of binutils is 2.25, which
> > supports XSAVE{,OPT,C,S} and XRSTOR{,S} instruction mnemonics.
> >
> > Replace the byte-wise specification of XSAVE{,OPT,C,S}
> > and XRSTOR{,S} with these proper mnemonics.
> >
> > No functional change intended.
> >
> > Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > Cc: Andy Lutomirski <luto@...nel.org>
> > Cc: Brian Gerst <brgerst@...il.com>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Link: https://lore.kernel.org/r/20250313130251.383204-1-ubizjak@gmail.com
> > ---
> >  arch/x86/kernel/fpu/xstate.h | 27 +++++++++++++--------------
> >  1 file changed, 13 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
> > index aa16f1a..1418423 100644
> > --- a/arch/x86/kernel/fpu/xstate.h
> > +++ b/arch/x86/kernel/fpu/xstate.h
> > @@ -94,18 +94,17 @@ static inline int update_pkru_in_sigframe(struct xregs_state __user *buf, u64 ma
> >  /* XSAVE/XRSTOR wrapper functions */
> >
> >  #ifdef CONFIG_X86_64
> > -#define REX_PREFIX   "0x48, "
> > +#define REX_SUFFIX   "64"
> >  #else
> > -#define REX_PREFIX
> > +#define REX_SUFFIX
> >  #endif
> >
> > -/* These macros all use (%edi)/(%rdi) as the single memory argument. */
> > -#define XSAVE                ".byte " REX_PREFIX "0x0f,0xae,0x27"
> > -#define XSAVEOPT     ".byte " REX_PREFIX "0x0f,0xae,0x37"
> > -#define XSAVEC               ".byte " REX_PREFIX "0x0f,0xc7,0x27"
> > -#define XSAVES               ".byte " REX_PREFIX "0x0f,0xc7,0x2f"
> > -#define XRSTOR               ".byte " REX_PREFIX "0x0f,0xae,0x2f"
> > -#define XRSTORS              ".byte " REX_PREFIX "0x0f,0xc7,0x1f"
> > +#define XSAVE                "xsave" REX_SUFFIX " %[xa]"
> > +#define XSAVEOPT     "xsaveopt" REX_SUFFIX " %[xa]"
> > +#define XSAVEC               "xsavec" REX_SUFFIX " %[xa]"
> > +#define XSAVES               "xsaves" REX_SUFFIX " %[xa]"
> > +#define XRSTOR               "xrstor" REX_SUFFIX " %[xa]"
> > +#define XRSTORS              "xrstors" REX_SUFFIX " %[xa]"
> >
> >  /*
> >   * After this @err contains 0 on success or the trap number when the
> > @@ -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.

Uros.