linux-kernel - Re: [PATCH RFC V4 09/10] x86/jump_label: use GENERIC_NOP5

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Date:	Fri, 14 Oct 2011 14:53:35 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	"David S. Miller" <davem@...emloft.net>,
	David Daney <david.daney@...ium.com>,
	Michael Ellerman <michael@...erman.id.au>,
	Jan Glauber <jang@...ux.vnet.ibm.com>,
	Jason Baron <jbaron@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH RFC V4 09/10] x86/jump_label: use GENERIC_NOP5_ATOMIC
 instead of jmp5 +0

On 10/13/2011 09:57 AM, Jeremy Fitzhardinge wrote:
> 
> Something like this?
> 
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> Date: Thu, 13 Oct 2011 09:55:25 -0700
> Subject: [PATCH] x86/nop: we can use P6 as generic NOP on 64-bit
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> 
> diff --git a/arch/x86/include/asm/nops.h b/arch/x86/include/asm/nops.h
> index 405b403..f9fead9 100644
> --- a/arch/x86/include/asm/nops.h
> +++ b/arch/x86/include/asm/nops.h
> @@ -19,15 +19,15 @@
>     6: leal 0x00000000(%esi),%esi
>     7: leal 0x00000000(,%esi,1),%esi
>  */
> -#define GENERIC_NOP1 0x90
> -#define GENERIC_NOP2 0x89,0xf6
> -#define GENERIC_NOP3 0x8d,0x76,0x00
> -#define GENERIC_NOP4 0x8d,0x74,0x26,0x00
> -#define GENERIC_NOP5 GENERIC_NOP1,GENERIC_NOP4
> -#define GENERIC_NOP6 0x8d,0xb6,0x00,0x00,0x00,0x00
> -#define GENERIC_NOP7 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00
> -#define GENERIC_NOP8 GENERIC_NOP1,GENERIC_NOP7
> -#define GENERIC_NOP5_ATOMIC NOP_DS_PREFIX,GENERIC_NOP4
> +#define GAS_NOP1 0x90
> +#define GAS_NOP2 0x89,0xf6
> +#define GAS_NOP3 0x8d,0x76,0x00
> +#define GAS_NOP4 0x8d,0x74,0x26,0x00
> +#define GAS_NOP5 GENERIC_NOP1,GENERIC_NOP4
> +#define GAS_NOP6 0x8d,0xb6,0x00,0x00,0x00,0x00
> +#define GAS_NOP7 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00
> +#define GAS_NOP8 GENERIC_NOP1,GENERIC_NOP7
> +#define GAS_NOP5_ATOMIC NOP_DS_PREFIX,GENERIC_NOP4
>  

They're not really the gas nops, either.  If you want to rename them I
would suggest GENERIC32_*

>  /* Opteron 64bit nops
>     1: nop
> @@ -87,6 +87,28 @@
>  #define P6_NOP8	0x0f,0x1f,0x84,0x00,0,0,0,0
>  #define P6_NOP5_ATOMIC P6_NOP5
>  
> +#ifdef CONFIG_X86_32
> +#define GENERIC_NOP1		GAS_NOP1
> +#define GENERIC_NOP2		GAS_NOP2
> +#define GENERIC_NOP3		GAS_NOP3
> +#define GENERIC_NOP4		GAS_NOP4
> +#define GENERIC_NOP5		GAS_NOP5
> +#define GENERIC_NOP6		GAS_NOP6
> +#define GENERIC_NOP7		GAS_NOP7
> +#define GENERIC_NOP8		GAS_NOP8
> +#define GENERIC_NOP5_ATOMIC	GAS_NOP5_ATOMIC
> +#else
> +#define GENERIC_NOP1		P6_NOP1
> +#define GENERIC_NOP2		P6_NOP2
> +#define GENERIC_NOP3		P6_NOP3
> +#define GENERIC_NOP4		P6_NOP4
> +#define GENERIC_NOP5		P6_NOP5
> +#define GENERIC_NOP6		P6_NOP6
> +#define GENERIC_NOP7		P6_NOP7
> +#define GENERIC_NOP8		P6_NOP8
> +#define GENERIC_NOP5_ATOMIC	P6_NOP5_ATOMIC
> +#endif
> +

Make sure you change all the downstream users too.

	-hpa

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