x86/idle: Disable IBRS when offlining cpu and re-enable on wakeup

CVE-2017-5715 (Spectre v2 Intel)

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>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 398e8324fea4e839289f1d3d396aa46fdd2dcd9c..a652bff7add4349092ba0e63bb9f1fa0979cb6a9 100644 (file)
--- 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 */