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 08/16] x86/speculation: Turn on or off STIBP according to a task's TIF_STIBP
Date: Tue, 20 Nov 2018 16:00:00 -0800 [thread overview]
Message-ID: <b6a7deb9f976680d5d96a2c1affc032604bb1879.1542757030.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 STIBP is used all the time, tasks that do not need STIBP
protection will get unnecessarily slowed down by STIBP.
To apply STIBP only to tasks that need it, a new task TIF_STIBP flag is
created. A x86 CPU uses STIBP only for tasks labeled with TIF_STIBP.
During context switch, this flag is checked and the STIBP bit in SPEC_CTRL
MSR is updated according to changes in this flag between previous and
next task.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
arch/x86/include/asm/msr-index.h | 6 +++++-
arch/x86/include/asm/spec-ctrl.h | 12 ++++++++++++
arch/x86/include/asm/thread_info.h | 5 ++++-
arch/x86/kernel/process.c | 14 +++++++++++++-
4 files changed, 34 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 80f4a4f..501c9d3 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -41,7 +41,11 @@
#define MSR_IA32_SPEC_CTRL 0x00000048 /* Speculation Control */
#define SPEC_CTRL_IBRS (1 << 0) /* Indirect Branch Restricted Speculation */
-#define SPEC_CTRL_STIBP (1 << 1) /* Single Thread Indirect Branch Predictors */
+#define SPEC_CTRL_STIBP_SHIFT 1 /*
+ * Single Thread Indirect Branch
+ * Predictor (STIBP) bit
+ */
+#define SPEC_CTRL_STIBP (1 << SPEC_CTRL_STIBP_SHIFT) /* STIBP mask */
#define SPEC_CTRL_SSBD_SHIFT 2 /* Speculative Store Bypass Disable bit */
#define SPEC_CTRL_SSBD (1 << SPEC_CTRL_SSBD_SHIFT) /* Speculative Store Bypass Disable */
diff --git a/arch/x86/include/asm/spec-ctrl.h b/arch/x86/include/asm/spec-ctrl.h
index 8e2f841..41b993e 100644
--- a/arch/x86/include/asm/spec-ctrl.h
+++ b/arch/x86/include/asm/spec-ctrl.h
@@ -53,12 +53,24 @@ static inline u64 ssbd_tif_to_spec_ctrl(u64 tifn)
return (tifn & _TIF_SSBD) >> (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);
}
+static inline u64 stibp_tif_to_spec_ctrl(u64 tifn)
+{
+ BUILD_BUG_ON(TIF_SPEC_INDIR_BRANCH < SPEC_CTRL_STIBP_SHIFT);
+ return (tifn & _TIF_SPEC_INDIR_BRANCH) >> (TIF_SPEC_INDIR_BRANCH - SPEC_CTRL_STIBP_SHIFT);
+}
+
static inline unsigned long ssbd_spec_ctrl_to_tif(u64 spec_ctrl)
{
BUILD_BUG_ON(TIF_SSBD < SPEC_CTRL_SSBD_SHIFT);
return (spec_ctrl & SPEC_CTRL_SSBD) << (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);
}
+static inline unsigned long stibp_spec_ctrl_to_tif(u64 spec_ctrl)
+{
+ BUILD_BUG_ON(TIF_SPEC_INDIR_BRANCH < SPEC_CTRL_STIBP_SHIFT);
+ return (spec_ctrl & SPEC_CTRL_STIBP) << (TIF_SPEC_INDIR_BRANCH - SPEC_CTRL_STIBP_SHIFT);
+}
+
static inline u64 ssbd_tif_to_amd_ls_cfg(u64 tifn)
{
return (tifn & _TIF_SSBD) ? x86_amd_ls_cfg_ssbd_mask : 0ULL;
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 2ff2a30..b3032c7 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -83,6 +83,7 @@ struct thread_info {
#define TIF_SYSCALL_EMU 6 /* syscall emulation active */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
+#define TIF_SPEC_INDIR_BRANCH 9 /* Indirect branch speculation restricted */
#define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */
#define TIF_UPROBE 12 /* breakpointed or singlestepping */
#define TIF_PATCH_PENDING 13 /* pending live patching update */
@@ -110,6 +111,7 @@ struct thread_info {
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
+#define _TIF_SPEC_INDIR_BRANCH (1 << TIF_SPEC_INDIR_BRANCH)
#define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
#define _TIF_UPROBE (1 << TIF_UPROBE)
#define _TIF_PATCH_PENDING (1 << TIF_PATCH_PENDING)
@@ -146,7 +148,8 @@ struct thread_info {
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW \
- (_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP|_TIF_SSBD)
+ (_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP| \
+ _TIF_SSBD|_TIF_SPEC_INDIR_BRANCH)
#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 74bef48..48fcd46 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -406,6 +406,8 @@ static __always_inline void spec_ctrl_update_msr(unsigned long tifn)
if (static_cpu_has(X86_FEATURE_SSBD))
msr |= ssbd_tif_to_spec_ctrl(tifn);
+ msr |= stibp_tif_to_spec_ctrl(tifn);
+
wrmsrl(MSR_IA32_SPEC_CTRL, msr);
}
@@ -418,7 +420,17 @@ static __always_inline void spec_ctrl_update_msr(unsigned long tifn)
static __always_inline void __speculation_ctrl_update(unsigned long tifp,
unsigned long tifn)
{
- bool updmsr = false;
+ bool updmsr;
+
+ /*
+ * Need STIBP defense against Spectre v2 attack
+ * if SMT is in use and enhanced IBRS is unsupported.
+ */
+ if (static_cpu_has(X86_FEATURE_STIBP) && cpu_use_smt_and_hotplug &&
+ !static_cpu_has(X86_FEATURE_USE_IBRS_ENHANCED))
+ updmsr = !!((tifp ^ tifn) & _TIF_SPEC_INDIR_BRANCH);
+ else
+ updmsr = false;
/* If TIF_SSBD is different, select the proper mitigation method */
if ((tifp ^ tifn) & _TIF_SSBD) {
--
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 ` [Patch v6 03/16] x86/speculation: Disable STIBP when enhanced IBRS is in use Tim Chen
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 ` Tim Chen [this message]
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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