linux-kernel - [tip:x86/asm] x86/entry/64: Use POP instead of MOV to restore regs on NMI return

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Message-ID: <tip-471ee4832209e986029b9fabdaad57b1eecb856b@git.kernel.org>
Date:   Thu, 2 Nov 2017 03:51:57 -0700
From:   tip-bot for Andy Lutomirski <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, hpa@...or.com, tglx@...utronix.de,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        luto@...nel.org, brgerst@...il.com, mingo@...nel.org,
        bpetkov@...e.de, dave.hansen@...el.com
Subject: [tip:x86/asm] x86/entry/64: Use POP instead of MOV to restore regs
 on NMI return

Commit-ID:  471ee4832209e986029b9fabdaad57b1eecb856b
Gitweb:     https://git.kernel.org/tip/471ee4832209e986029b9fabdaad57b1eecb856b
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Thu, 2 Nov 2017 00:59:05 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 2 Nov 2017 11:04:40 +0100

x86/entry/64: Use POP instead of MOV to restore regs on NMI return

This gets rid of the last user of the old RESTORE_..._REGS infrastructure.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bpetkov@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/652a260f17a160789bc6a41d997f98249b73e2ab.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/entry_64.S | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index b5a0ea6..5b2f0bc 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1559,11 +1559,14 @@ end_repeat_nmi:
 nmi_swapgs:
 	SWAPGS_UNSAFE_STACK
 nmi_restore:
-	RESTORE_EXTRA_REGS
-	RESTORE_C_REGS
+	POP_EXTRA_REGS
+	POP_C_REGS
 
-	/* Point RSP at the "iret" frame. */
-	REMOVE_PT_GPREGS_FROM_STACK 6*8
+	/*
+	 * Skip orig_ax and the "outermost" frame to point RSP at the "iret"
+	 * at the "iret" frame.
+	 */
+	addq	$6*8, %rsp
 
 	/*
 	 * Clear "NMI executing".  Set DF first so that we can easily