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

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Message-ID: <4E97188A.6040400@goop.org>
Date:	Thu, 13 Oct 2011 09:57:46 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
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 08:40 AM, H. Peter Anvin wrote:
> On 10/12/2011 05:08 PM, Jeremy Fitzhardinge wrote:
>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
>>
>> GENERIC_NOP5_ATOMIC should make a better nop.
>>
> On 32 bits, yes.  On 64 bits you should use P6_NOP5_ATOMIC.

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
 
 /* 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
+
 #define _ASM_MK_NOP(x) ".byte " __stringify(x) "\n"
 
 #if defined(CONFIG_MK7)


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