From 2238246ff8d533a5f2327d1f953375876d8a013c Mon Sep 17 00:00:00 2001
From: Xiaoyao Li <xiaoyao.li@linux.intel.com>
Date: Thu, 27 Jun 2019 12:55:25 +0800
Subject: [PATCH] x86/boot: Make the GDT 8-byte aligned

The segment descriptors are loaded with an implicitly LOCK-ed instruction,
which could trigger the split lock #AC exception if the variable is not
properly aligned and crosses a cache line.

Align the GDT properly so the descriptors are all 8 byte aligned.

Signed-off-by: Xiaoyao Li <xiaoyao.li@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lkml.kernel.org/r/20190627045525.105266-1-xiaoyao.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/boot/compressed/head_64.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index fafb75c6c592..6233ae35d0d9 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -659,6 +659,7 @@ no_longmode:
 gdt64:
 	.word	gdt_end - gdt
 	.quad   0
+	.balign	8
 gdt:
 	.word	gdt_end - gdt
 	.long	gdt