Commit 34bce7c9 authored Nov 25, 2018 by Tim Chen Committed by Thomas Gleixner Nov 28, 2018

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

parent a8f76ae4

arch/x86/kernel/cpu/bugs.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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

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