From 4963d177f90d0ce4a63c0dcdb86acc9fd4919fca Mon Sep 17 00:00:00 2001
From: Tim Chen <tim.c.chen@linux.intel.com>
Date: Thu, 21 Dec 2017 20:24:24 -0500
Subject: [PATCH] x86/idle: Disable IBRS when offlining cpu and re-enable on
 wakeup

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


Orabug: 27344012
CVE: CVE-2017-5715

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.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 757546dffb0b..9495f5efdf87 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -76,6 +76,7 @@
 #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;
@@ -1504,9 +1505,15 @@ 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 */
-- 
2.50.1