Commit-ID: 34bce7c9690b1d897686aac89604ba7adc365556 Gitweb: https://git.kernel.org/tip/34bce7c9690b1d897686aac89604ba7adc365556 Author: Tim Chen <[email protected]> AuthorDate: Sun, 25 Nov 2018 19:33:33 +0100 Committer: Thomas Gleixner <[email protected]> CommitDate: Wed, 28 Nov 2018 11:57:05 +0100
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 <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Reviewed-by: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Jiri Kosina <[email protected]> Cc: Tom Lendacky <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Casey Schaufler <[email protected]> Cc: Asit Mallick <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: Jon Masters <[email protected]> Cc: Waiman Long <[email protected]> Cc: Greg KH <[email protected]> Cc: Dave Stewart <[email protected]> Cc: Kees Cook <[email protected]> Cc: [email protected] Link: https://lkml.kernel.org/r/[email protected] --- arch/x86/kernel/cpu/bugs.c | 7 +++++++ 1 file changed, 7 insertions(+) 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
