Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Thu, 16 May 2019 16:55:33 +0100 | Subject | [PATCH 3.16 38/86] x86/speculation: Disable STIBP when enhanced IBRS is in use |
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3.16.68-rc1 review patch. If anyone has any objections, please let me know.
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From: Tim Chen <tim.c.chen@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.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> Link: https://lkml.kernel.org/r/20181125185003.966801480@linutronix.de Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- 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 @@ -380,6 +380,10 @@ 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; @@ -823,6 +827,9 @@ static void __init l1tf_select_mitigatio 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
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