From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Tim Chen <tim.c.chen@linux.intel.com>
Date: Wed, 15 Nov 2017 12:24:19 -0800
Subject: [PATCH] x86/idle: Disable IBRS when offlining cpu and re-enable on
 wakeup
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CVE-2017-5753
CVE-2017-5715

Clear IBRS when cpu is offlined and set it when brining it back online.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit 9bcf662c1690880b2464fe99d0f58dce53c0d89f)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 arch/x86/kernel/smpboot.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 398e8324fea4..a652bff7add4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -77,6 +77,7 @@
 #include <asm/i8259.h>
 #include <asm/realmode.h>
 #include <asm/misc.h>
+#include <asm/microcode.h>
 
 /* Number of siblings per CPU package */
 int smp_num_siblings = 1;
@@ -1692,9 +1693,15 @@ void native_play_dead(void)
 	play_dead_common();
 	tboot_shutdown(TB_SHUTDOWN_WFS);
 
+	if (boot_cpu_has(X86_FEATURE_SPEC_CTRL))
+		native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
+
 	mwait_play_dead();	/* Only returns on failure */
 	if (cpuidle_play_dead())
 		hlt_play_dead();
+
+	if (boot_cpu_has(X86_FEATURE_SPEC_CTRL))
+		native_wrmsrl(MSR_IA32_SPEC_CTRL, FEATURE_ENABLE_IBRS);
 }
 
 #else /* ... !CONFIG_HOTPLUG_CPU */
-- 
2.14.2

