linux-kernel - Re: [PATCH] x86/boot: Use __ASM_SIZE() to reduce ifdeffery in cpuflags.c

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Message-ID: <CAFULd4bVO39emR49thto4w6LZX0vS9eJKE75u26aCFk7CRVrVw@mail.gmail.com>
Date: Thu, 18 Jul 2024 08:46:57 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH] x86/boot: Use __ASM_SIZE() to reduce ifdeffery in cpuflags.c

On Thu, Jul 18, 2024 at 8:36 AM H. Peter Anvin <hpa@...or.com> wrote:
>
> On July 17, 2024 11:32:18 PM PDT, Uros Bizjak <ubizjak@...il.com> wrote:
> >Use __ASM_SIZE() macro to add correct insn suffix to pushf/popf.
> >
> >Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> >Cc: Thomas Gleixner <tglx@...utronix.de>
> >Cc: Ingo Molnar <mingo@...nel.org>
> >Cc: Borislav Petkov <bp@...en8.de>
> >Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> >Cc: "H. Peter Anvin" <hpa@...or.com>
> >---
> > arch/x86/boot/cpuflags.c | 10 +++-------
> > 1 file changed, 3 insertions(+), 7 deletions(-)
> >
> >diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
> >index d75237ba7ce9..aacabe431fd5 100644
> >--- a/arch/x86/boot/cpuflags.c
> >+++ b/arch/x86/boot/cpuflags.c
> >@@ -2,6 +2,7 @@
> > #include <linux/types.h>
> > #include "bitops.h"
> >
> >+#include <asm/asm.h>
> > #include <asm/processor-flags.h>
> > #include <asm/required-features.h>
> > #include <asm/msr-index.h>
> >@@ -36,13 +37,8 @@ static int has_fpu(void)
> >  * compressed/ directory where it may be 64-bit code, and thus needs
> >  * to be 'pushfq' or 'popfq' in that case.
> >  */
> >-#ifdef __x86_64__
> >-#define PUSHF "pushfq"
> >-#define POPF "popfq"
> >-#else
> >-#define PUSHF "pushfl"
> >-#define POPF "popfl"
> >-#endif
> >+#define PUSHF __ASM_SIZE(pushf)
> >+#define POPF __ASM_SIZE(popf)
> >
> > int has_eflag(unsigned long mask)
> > {
>
> Just use pushf/popf. gas hasn't needed that suffix for a long time as far as I know.

Yes, this works, too. So I guess we can also remove the comment
explaining the reason for explicit suffixes?

Thanks,
Uros.