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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
This commit is contained in:
Tim Chen 2018-11-25 19:33:33 +01:00 committed by Thomas Gleixner
parent a8f76ae41c
commit 34bce7c969
1 changed files with 7 additions and 0 deletions
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7
arch/x86/kernel/cpu/bugs.c
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@ -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