linux-kernel - [PATCH 4.14 042/159] x86/entry/64: Use POP instead of MOV to restore regs on NMI return

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Date:   Fri, 22 Dec 2017 09:45:27 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.14 042/159] x86/entry/64: Use POP instead of MOV to restore regs on NMI return

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@...nel.org>

commit 471ee4832209e986029b9fabdaad57b1eecb856b upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/entry/entry_64.S |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1560,11 +1560,14 @@ 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