linux-kernel - [PATCH 4/6] x86/entry: Remove skip

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Date:   Fri, 06 May 2022 14:14:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        jpoimboe@...hat.com, brgerst@...il.com, jiangshanlai@...il.com,
        Andrew.Cooper3@...rix.com, mark.rutland@....com
Subject: [PATCH 4/6] x86/entry: Remove skip_r11rcx

Yes, r11 and rcx have been restored previously, but since we're
popping them anyway (into rsi) might as well pop them into their own
regs -- setting them to the value they already are.

Less magical code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/entry/calling.h  |   10 +---------
 arch/x86/entry/entry_64.S |    3 +--
 2 files changed, 2 insertions(+), 11 deletions(-)

--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -120,27 +120,19 @@ For 32-bit we have the following convent
 	CLEAR_REGS
 .endm
 
-.macro POP_REGS pop_rdi=1 skip_r11rcx=0
+.macro POP_REGS pop_rdi=1
 	popq %r15
 	popq %r14
 	popq %r13
 	popq %r12
 	popq %rbp
 	popq %rbx
-	.if \skip_r11rcx
-	popq %rsi
-	.else
 	popq %r11
-	.endif
 	popq %r10
 	popq %r9
 	popq %r8
 	popq %rax
-	.if \skip_r11rcx
-	popq %rsi
-	.else
 	popq %rcx
-	.endif
 	popq %rdx
 	popq %rsi
 	.if \pop_rdi
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -191,8 +191,7 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h
 	 * perf profiles. Nothing jumps here.
 	 */
 syscall_return_via_sysret:
-	/* rcx and r11 are already restored (see code above) */
-	POP_REGS pop_rdi=0 skip_r11rcx=1
+	POP_REGS pop_rdi=0
 
 	/*
 	 * Now all regs are restored except RSP and RDI.