linux-kernel - Re: [PATCH] x86: Use INVPCID mnemonic in invpcid.h

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Date:   Sat, 9 May 2020 13:33:07 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Uros Bizjak <ubizjak@...il.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: Use INVPCID mnemonic in invpcid.h

On Fri, May 08, 2020 at 11:22:47AM +0200, Uros Bizjak wrote:
> Current minimum required version of binutils is 2.23,
> which supports INVPCID instruction mnemonic.
> 
> Replace the byte-wise specification of INVPCID with
> this proper mnemonic.
> 
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/include/asm/invpcid.h | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/invpcid.h b/arch/x86/include/asm/invpcid.h
> index 989cfa86de85..23749bbca0ad 100644
> --- a/arch/x86/include/asm/invpcid.h
> +++ b/arch/x86/include/asm/invpcid.h
> @@ -12,12 +12,9 @@ static inline void __invpcid(unsigned long pcid, unsigned long addr,
>  	 * stale TLB entries and, especially if we're flushing global
>  	 * mappings, we don't want the compiler to reorder any subsequent
>  	 * memory accesses before the TLB flush.
> -	 *
> -	 * The hex opcode is invpcid (%ecx), %eax in 32-bit mode and
> -	 * invpcid (%rcx), %rax in long mode.
>  	 */
> -	asm volatile (".byte 0x66, 0x0f, 0x38, 0x82, 0x01"
> -		      : : "m" (desc), "a" (type), "c" (&desc) : "memory");
> +	asm volatile ("invpcid %1, %0"
> +		      : : "r" (type), "m" (desc) : "memory");

How about I make it even more readable when applying?

        asm volatile("invpcid %[desc], %[type]"
                     :: [desc] "m" (desc), [type] "r" (type) : "memory");

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette