linux-kernel - [RFC 26/30] x86/asm: Remove thread_info.sysenter

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Message-Id: <6bcf44de7d146d1b98535c52a432185295d7a9db.1441146105.git.luto@kernel.org>
Date:	Tue,  1 Sep 2015 15:41:26 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC 26/30] x86/asm: Remove thread_info.sysenter_return

It's no longer needed.

We could reinstate something like it as an optimization, which would
remove two cachelines from the fast syscall entry working set.  I
benchmarked it, and it makes no difference whatsoever to the
performance of cache-hot compat syscalls on Sandy Bridge.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/thread_info.h | 1 -
 arch/x86/kernel/asm-offsets.c      | 3 ---
 2 files changed, 4 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 8afdc3e44247..a1ecd214d227 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -59,7 +59,6 @@ struct thread_info {
 	__u32			cpu;		/* current CPU */
 	int			saved_preempt_count;
 	mm_segment_t		addr_limit;
-	void __user		*sysenter_return;
 	unsigned int		sig_on_uaccess_error:1;
 	unsigned int		uaccess_err:1;	/* uaccess failed */
 };
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 8e3d22a1af94..95a18e25d5bf 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -54,9 +54,6 @@ void common(void) {
 	OFFSET(IA32_SIGCONTEXT_ip, sigcontext_ia32, ip);
 
 	BLANK();
-	OFFSET(TI_sysenter_return, thread_info, sysenter_return);
-
-	BLANK();
 	OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe_ia32, uc.uc_mcontext);
 #endif
 
-- 
2.4.3

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