linux-kernel - [PATCH v2 08/20] x86/entry/64: Use POP instead of MOV to restore regs on NMI return

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Date:   Thu,  2 Nov 2017 00:59:05 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     X86 ML <x86@...nel.org>
Cc:     Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 08/20] 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>
---
 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 2e7f4952af94..f0f842124aa9 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
-- 
2.13.6