[Xen-devel] Re: [PATCH RFC V4 09/10] x86/jump_label: use GENERIC_NOP5_ATOMIC instead of jmp5 +0

["H. Peter Anvin" <hpa@xxxxxxxxx>]

On 10/13/2011 09:57 AM, Jeremy Fitzhardinge wrote:
> 
> Something like this?
> 
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> 
> 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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