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Message-ID: <20220915111146.539578813@infradead.org>
Date: Thu, 15 Sep 2022 13:11:14 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, x86@...nel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Andrew Cooper <Andrew.Cooper3@...rix.com>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Johannes Wikner <kwikner@...z.ch>,
Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
Joao Moreira <joao.moreira@...el.com>,
Joseph Nuzman <joseph.nuzman@...el.com>,
Steven Rostedt <rostedt@...dmis.org>,
Juergen Gross <jgross@...e.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
K Prateek Nayak <kprateek.nayak@....com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v3 35/59] x86/entry: Make sync_regs() invocation a tail call
From: Peter Zijlstra <peterz@...radead.org>
No point in having a call there. Spare the call/ret overhead.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
arch/x86/entry/entry_64.S | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1062,11 +1062,8 @@ SYM_CODE_START_LOCAL(error_entry)
UNTRAIN_RET
leaq 8(%rsp), %rdi /* arg0 = pt_regs pointer */
-.Lerror_entry_from_usermode_after_swapgs:
-
/* Put us onto the real thread stack. */
- call sync_regs
- RET
+ jmp sync_regs
/*
* There are two places in the kernel that can potentially fault with
@@ -1124,7 +1121,7 @@ SYM_CODE_START_LOCAL(error_entry)
leaq 8(%rsp), %rdi /* arg0 = pt_regs pointer */
call fixup_bad_iret
mov %rax, %rdi
- jmp .Lerror_entry_from_usermode_after_swapgs
+ jmp sync_regs
SYM_CODE_END(error_entry)
SYM_CODE_START_LOCAL(error_return)
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