lkml.org 
[lkml]   [2018]   [Nov]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[patch 05/24] x86/speculation: Disable STIBP when enhanced IBRS is in use
From: Tim Chen <tim.c.chen@linux.intel.com>

If enhanced IBRS is active, STIBP is redundant for mitigating Spectre v2
user space exploits from hyperthread sibling.

Disable STIBP when enhanced IBRS is used.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
arch/x86/kernel/cpu/bugs.c | 7 +++++++
1 file changed, 7 insertions(+)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -321,6 +321,10 @@ static bool stibp_needed(void)
if (spectre_v2_enabled == SPECTRE_V2_NONE)
return false;

+ /* Enhanced IBRS makes using STIBP unnecessary. */
+ if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+ return false;
+
if (!boot_cpu_has(X86_FEATURE_STIBP))
return false;

@@ -846,6 +850,9 @@ static ssize_t l1tf_show_state(char *buf

static char *stibp_state(void)
{
+ if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+ return "";
+
if (x86_spec_ctrl_base & SPEC_CTRL_STIBP)
return ", STIBP";
else

\
 
 \ /
  Last update: 2018-11-21 21:21    [W:0.559 / U:0.536 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site