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authorTim Chen <tim.c.chen@linux.intel.com>2018-11-25 19:33:33 +0100
committerThomas Gleixner <tglx@linutronix.de>2018-11-28 11:57:05 +0100
commit34bce7c9690b1d897686aac89604ba7adc365556 (patch)
treee50d5a1a628e1d7c76c2d582dc54aed757844e9e /arch
parenta8f76ae41cd633ac00be1b3019b1eb4741be3828 (diff)
x86/speculation: Disable STIBP when enhanced IBRS is in use
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> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Casey Schaufler <casey.schaufler@intel.com> Cc: Asit Mallick <asit.k.mallick@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jon Masters <jcm@redhat.com> Cc: Waiman Long <longman9394@gmail.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Dave Stewart <david.c.stewart@intel.com> Cc: Kees Cook <keescook@chromium.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185003.966801480@linutronix.de
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/bugs.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index a1502bce9eb8..924cd06dd43b 100644
--- 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