4.19-stable review patch. If anyone has any objections, please let me know.
------------------ From: Tim Chen tim.c.c...@linux.intel.com commit 34bce7c9690b1d897686aac89604ba7adc365556 upstream 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.c...@linux.intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Reviewed-by: Ingo Molnar <mi...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Jiri Kosina <jkos...@suse.cz> Cc: Tom Lendacky <thomas.lenda...@amd.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Andrea Arcangeli <aarca...@redhat.com> Cc: David Woodhouse <d...@amazon.co.uk> Cc: Andi Kleen <a...@linux.intel.com> Cc: Dave Hansen <dave.han...@intel.com> Cc: Casey Schaufler <casey.schauf...@intel.com> Cc: Asit Mallick <asit.k.mall...@intel.com> Cc: Arjan van de Ven <ar...@linux.intel.com> Cc: Jon Masters <j...@redhat.com> Cc: Waiman Long <longman9...@gmail.com> Cc: Greg KH <gre...@linuxfoundation.org> Cc: Dave Stewart <david.c.stew...@intel.com> Cc: Kees Cook <keesc...@chromium.org> Cc: sta...@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185003.966801...@linutronix.de Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- 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 @@ -320,6 +320,10 @@ 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; @@ -844,6 +848,9 @@ 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
