From: Tim Chen <tim.c.chen@linux.intel.com>
To: Jiri Kosina <jikos@kernel.org>, Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Andi Kleen <ak@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Casey Schaufler <casey.schaufler@intel.com>,
Asit Mallick <asit.k.mallick@intel.com>,
Arjan van de Ven <arjan@linux.intel.com>,
Jon Masters <jcm@redhat.com>, Waiman Long <longman9394@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Dave Stewart <david.c.stewart@intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
stable@vger.kernel.org
Subject: [Patch v6 03/16] x86/speculation: Disable STIBP when enhanced IBRS is in use
Date: Tue, 20 Nov 2018 15:59:55 -0800 [thread overview]
Message-ID: <98459d97781796d8fa04aecb7ed473b7c4e48956.1542757030.git.tim.c.chen@linux.intel.com> (raw)
In-Reply-To: <cover.1542757030.git.tim.c.chen@linux.intel.com>
In-Reply-To: <cover.1542757030.git.tim.c.chen@linux.intel.com>
If enhanced IBRS is engaged, STIBP is redundant in 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>
---
arch/x86/kernel/cpu/bugs.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 3a6f13b..199f27e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -323,11 +323,16 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
return cmd;
}
+/* Determine if STIBP should be always on. */
static bool stibp_needed(void)
{
if (spectre_v2_enabled == SPECTRE_V2_NONE)
return false;
+ /* Using enhanced IBRS makes using STIBP unnecessary. */
+ if (static_cpu_has(X86_FEATURE_USE_IBRS_ENHANCED))
+ return false;
+
if (!boot_cpu_has(X86_FEATURE_STIBP))
return false;
@@ -856,6 +861,9 @@ 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
--
2.9.4
next prev parent reply other threads:[~2018-11-21 0:33 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-20 23:59 [Patch v6 00/16] Provide task property based options to enable Spectre v2 userspace-userspace protection Tim Chen
2018-11-20 23:59 ` [Patch v6 01/16] x86/speculation: Reorganize cpu_show_common() Tim Chen
2018-11-20 23:59 ` [Patch v6 02/16] x86/speculation: Add X86_FEATURE_USE_IBRS_ENHANCED Tim Chen
2018-11-20 23:59 ` Tim Chen [this message]
2018-11-20 23:59 ` [Patch v6 04/16] x86/speculation: Rename SSBD update functions Tim Chen
2018-11-20 23:59 ` [Patch v6 05/16] x86/speculation: Reorganize speculation control MSRs update Tim Chen
2018-11-20 23:59 ` [Patch v6 06/16] smt: Create cpu_smt_enabled static key for SMT specific code Tim Chen
2018-11-20 23:59 ` [Patch v6 07/16] x86/smt: Convert cpu_smt_control check to cpu_smt_enabled static key Tim Chen
2018-11-21 0:00 ` [Patch v6 08/16] x86/speculation: Turn on or off STIBP according to a task's TIF_STIBP Tim Chen
2018-11-21 0:00 ` [Patch v6 09/16] x86/speculation: Add Spectre v2 app to app protection modes Tim Chen
2018-11-21 0:00 ` [Patch v6 10/16] x86/speculation: Create PRCTL interface to restrict indirect branch speculation Tim Chen
2018-11-21 0:00 ` [Patch v6 11/16] x86/speculation: Enable IBPB for tasks with TIF_SPEC_BRANCH_SPECULATION Tim Chen
2018-11-21 0:00 ` [Patch v6 12/16] x86/speculation: Add 'seccomp' Spectre v2 app to app protection mode Tim Chen
2018-11-21 0:44 ` Jiri Kosina
2018-11-21 0:54 ` Tim Chen
2018-11-21 0:00 ` [Patch v6 13/16] security: Update speculation restriction of a process when modifying its dumpability Tim Chen
2018-11-21 0:00 ` [Patch v6 14/16] x86/speculation: Use STIBP to restrict speculation on non-dumpable task Tim Chen
2018-11-21 1:27 ` Linus Torvalds
2018-11-21 6:14 ` Jiri Kosina
2018-11-21 17:41 ` Tim Chen
2018-11-21 19:32 ` Linus Torvalds
2018-11-21 20:07 ` Dave Hansen
2018-11-21 20:26 ` Linus Torvalds
2018-11-21 0:00 ` [Patch v6 15/16] sched/smt: Make sched_smt_present track topology Tim Chen
2018-11-21 0:00 ` [Patch v6 16/16] x86/smt: Allow disabling of SMT when last SMT is offlined Tim Chen
2018-11-21 0:44 ` [Patch v6 00/16] Provide task property based options to enable Spectre v2 userspace-userspace protection Tim Chen
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