From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jiri Kosina <jkosina@suse.cz>,
Tom Lendacky <thomas.lendacky@amd.com>,
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>,
Kees Cook <keescook@chromium.org>,
Tim Chen <tim.c.chen@linux.intel.com>
Subject: Re: [patch 16/24] x86/speculation: Prepare for per task indirect branch speculation control
Date: Thu, 22 Nov 2018 08:57:09 +0100 [thread overview]
Message-ID: <20181122075709.GH41788@gmail.com> (raw)
In-Reply-To: <20181121201723.856044561@linutronix.de>
* Thomas Gleixner <tglx@linutronix.de> wrote:
> From: Tim Chen <tim.c.chen@linux.intel.com>
>
> To avoid the overhead of STIBP always on, it's necessary to allow per task
> control of STIBP.
>
> Add a new task flag TIF_SPEC_IB and evaluate it during context switch if
> SMT is active and flag evaluation is enabled by the speculation control
> code. Add the conditional evaluation to x86_virt_spec_ctrl() as well so the
> guest/host switch works properly.
>
> This has no effect because TIF_SPEC_IB cannot be set yet and the static key
> which controls evaluation is off. Preparatory patch for adding the control
> code.
>
> [ tglx: Simplify the context switch logic and make the TIF evaluation
> depend on SMP=y and on the static key controlling the conditional
> update. Rename it to TIF_SPEC_IB because it controls both STIBP and
> IBPB ]
>
> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
> ---
> arch/x86/include/asm/msr-index.h | 5 +++--
> arch/x86/include/asm/spec-ctrl.h | 12 ++++++++++++
> arch/x86/include/asm/thread_info.h | 5 ++++-
> arch/x86/kernel/cpu/bugs.c | 4 ++++
> arch/x86/kernel/process.c | 24 ++++++++++++++++++++++--
> 5 files changed, 45 insertions(+), 5 deletions(-)
>
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -41,9 +41,10 @@
>
> #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 */
> +#define SPEC_CTRL_SSBD (1 << SPEC_CTRL_SSBD_SHIFT) /* Speculative Store Bypass Disable */
>
> #define MSR_IA32_PRED_CMD 0x00000049 /* Prediction Command */
> #define PRED_CMD_IBPB (1 << 0) /* Indirect Branch Prediction Barrier */
> --- 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(
> 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_IB < SPEC_CTRL_STIBP_SHIFT);
> + return (tifn & _TIF_SPEC_IB) >> (TIF_SPEC_IB - 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_IB < SPEC_CTRL_STIBP_SHIFT);
> + return (spec_ctrl & SPEC_CTRL_STIBP) << (TIF_SPEC_IB - 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;
> --- 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_IB 9 /* Indirect branch speculation mitigation */
> #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_IB (1 << TIF_SPEC_IB)
> #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_IB)
>
> #define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
> #define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -148,6 +148,10 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl,
> static_cpu_has(X86_FEATURE_AMD_SSBD))
> hostval |= ssbd_tif_to_spec_ctrl(ti->flags);
>
> + /* Check whether dynamic indirect branch control is on */
> + if (static_branch_unlikely(&switch_to_cond_stibp))
> + hostval |= stibp_tif_to_spec_ctrl(ti->flags);
> +
> if (hostval != guestval) {
> msrval = setguest ? guestval : hostval;
> wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -12,6 +12,7 @@
> #include <linux/sched/debug.h>
> #include <linux/sched/task.h>
> #include <linux/sched/task_stack.h>
> +#include <linux/sched/topology.h>
> #include <linux/init.h>
> #include <linux/export.h>
> #include <linux/pm.h>
> @@ -406,6 +407,11 @@ static __always_inline void spec_ctrl_up
> if (static_cpu_has(X86_FEATURE_SSBD))
> msr |= ssbd_tif_to_spec_ctrl(tifn);
>
> + /* Only evaluate STIBP if dynamic control is enabled */
> + if (IS_ENABLED(CONFIG_SMP) &&
> + static_branch_unlikely(&switch_to_cond_stibp))
> + msr |= stibp_tif_to_spec_ctrl(tifn);
> + /*
> + * Only evaluate TIF_SPEC_IB if dynamic control is
> + * enabled, otherwise avoid the MSR write
> + */
> + if (IS_ENABLED(CONFIG_SMP) &&
> + static_branch_unlikely(&switch_to_cond_stibp))
> + updmsr |= !!(tif_diff & _TIF_SPEC_IB);
Small nit:
we use several terms here in an interchangeable fashion:
- 'dynamic control'
- 'conditional STIBP'
The in-code variable naming follows the second nomenclature, while we
often mention 'dynamic control' - and the relationship is not always
obvious immediately.
It might make sense to pick one of these - for example if we pick
'conditional STIBP' then the second comment would become:
/*
* Only evaluate TIF_SPEC_IB if conditional STIBP is
* enabled, otherwise avoid the MSR write
*/
etc.
Thanks,
ngo
next prev parent reply other threads:[~2018-11-22 7:57 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-21 20:14 [patch 00/24] x86/speculation: Remedy the STIBP/IBPB overhead Thomas Gleixner
2018-11-21 20:14 ` [patch 01/24] x86/speculation: Update the TIF_SSBD comment Thomas Gleixner
2018-11-21 20:28 ` Linus Torvalds
2018-11-21 20:30 ` Thomas Gleixner
2018-11-21 20:33 ` Linus Torvalds
2018-11-21 22:48 ` Thomas Gleixner
2018-11-21 22:53 ` Borislav Petkov
2018-11-21 22:55 ` Thomas Gleixner
2018-11-21 22:55 ` Arjan van de Ven
2018-11-21 22:56 ` Borislav Petkov
2018-11-21 23:07 ` Borislav Petkov
2018-11-21 23:04 ` Josh Poimboeuf
2018-11-21 23:08 ` Borislav Petkov
2018-11-22 17:30 ` Josh Poimboeuf
2018-11-22 17:52 ` Borislav Petkov
2018-11-22 21:17 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 02/24] x86/speculation: Clean up spectre_v2_parse_cmdline() Thomas Gleixner
2018-11-21 20:14 ` [patch 03/24] x86/speculation: Remove unnecessary ret variable in cpu_show_common() Thomas Gleixner
2018-11-21 20:14 ` [patch 04/24] x86/speculation: Reorganize cpu_show_common() Thomas Gleixner
2018-11-21 20:14 ` [patch 05/24] x86/speculation: Disable STIBP when enhanced IBRS is in use Thomas Gleixner
2018-11-21 20:33 ` Borislav Petkov
2018-11-21 20:36 ` Thomas Gleixner
2018-11-21 22:01 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 06/24] x86/speculation: Rename SSBD update functions Thomas Gleixner
2018-11-21 20:14 ` [patch 07/24] x86/speculation: Reorganize speculation control MSRs update Thomas Gleixner
2018-11-21 20:14 ` [patch 08/24] sched/smt: Make sched_smt_present track topology Thomas Gleixner
2018-11-21 20:14 ` [patch 09/24] x86/Kconfig: Select SCHED_SMT if SMP enabled Thomas Gleixner
2018-11-21 20:14 ` [patch 10/24] sched/smt: Expose sched_smt_present static key Thomas Gleixner
2018-11-21 20:41 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 11/24] x86/speculation: Rework SMT state change Thomas Gleixner
2018-11-21 20:14 ` [patch 12/24] x86/l1tf: Show actual SMT state Thomas Gleixner
2018-11-21 20:14 ` [patch 13/24] x86/speculation: Reorder the spec_v2 code Thomas Gleixner
2018-11-21 20:14 ` [patch 14/24] x86/speculation: Unify conditional spectre v2 print functions Thomas Gleixner
2018-11-22 7:59 ` Ingo Molnar
2018-11-21 20:14 ` [patch 15/24] x86/speculation: Add command line control for indirect branch speculation Thomas Gleixner
2018-11-21 23:43 ` Borislav Petkov
2018-11-22 8:14 ` Thomas Gleixner
2018-11-22 9:07 ` Thomas Gleixner
2018-11-22 9:18 ` Peter Zijlstra
2018-11-22 10:10 ` Borislav Petkov
2018-11-22 10:48 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 16/24] x86/speculation: Prepare for per task indirect branch speculation control Thomas Gleixner
2018-11-22 7:57 ` Ingo Molnar [this message]
2018-11-21 20:14 ` [patch 17/24] x86/speculation: Move IBPB control out of switch_mm() Thomas Gleixner
2018-11-22 0:01 ` Andi Kleen
2018-11-22 7:42 ` Jiri Kosina
2018-11-22 9:18 ` Thomas Gleixner
2018-11-22 1:40 ` Tim Chen
2018-11-22 7:52 ` Ingo Molnar
2018-11-22 22:29 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 18/24] x86/speculation: Avoid __switch_to_xtra() calls Thomas Gleixner
2018-11-22 1:23 ` Tim Chen
2018-11-22 7:44 ` Ingo Molnar
2018-11-21 20:14 ` [patch 19/24] ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS Thomas Gleixner
2018-11-21 20:14 ` [patch 20/24] x86/speculation: Split out TIF update Thomas Gleixner
2018-11-22 2:13 ` Tim Chen
2018-11-22 23:00 ` Thomas Gleixner
2018-11-23 7:37 ` Ingo Molnar
2018-11-26 18:35 ` Tim Chen
2018-11-26 21:55 ` Thomas Gleixner
2018-11-27 7:05 ` Jiri Kosina
2018-11-27 7:13 ` Thomas Gleixner
2018-11-27 7:30 ` Jiri Kosina
2018-11-27 12:52 ` Jiri Kosina
2018-11-27 13:18 ` Jiri Kosina
2018-11-27 21:57 ` Thomas Gleixner
2018-11-27 22:07 ` Jiri Kosina
2018-11-27 22:20 ` Jiri Kosina
2018-11-27 22:36 ` Thomas Gleixner
2018-11-28 1:50 ` Tim Chen
2018-11-28 10:43 ` Thomas Gleixner
2018-11-28 6:05 ` Jiri Kosina
2018-11-28 14:33 ` [tip:x86/pti] x86/speculation: Prevent stale SPEC_CTRL msr content tip-bot for Thomas Gleixner
2018-11-22 7:43 ` [patch 20/24] x86/speculation: Split out TIF update Ingo Molnar
2018-11-22 23:04 ` Thomas Gleixner
2018-11-23 7:37 ` Ingo Molnar
2018-11-21 20:14 ` [patch 21/24] x86/speculation: Prepare arch_smt_update() for PRCTL mode Thomas Gleixner
2018-11-22 7:34 ` Ingo Molnar
2018-11-22 23:17 ` Thomas Gleixner
2018-11-22 23:28 ` Jiri Kosina
2018-11-21 20:14 ` [patch 22/24] x86/speculation: Create PRCTL interface to restrict indirect branch speculation Thomas Gleixner
2018-11-22 7:10 ` Ingo Molnar
2018-11-22 9:03 ` Peter Zijlstra
2018-11-22 9:08 ` Thomas Gleixner
2018-11-22 12:26 ` Borislav Petkov
2018-11-22 12:33 ` Peter Zijlstra
2018-11-21 20:14 ` [patch 23/24] x86/speculation: Enable PRCTL mode for spectre_v2_app2app Thomas Gleixner
2018-11-22 7:17 ` Ingo Molnar
2018-11-21 20:14 ` [patch 24/24] x86/speculation: Add seccomp Spectre v2 app to app protection mode Thomas Gleixner
2018-11-22 2:24 ` Tim Chen
2018-11-22 7:26 ` Ingo Molnar
2018-11-22 23:45 ` Thomas Gleixner
2018-11-21 23:48 ` [patch 00/24] x86/speculation: Remedy the STIBP/IBPB overhead Tim Chen
2018-11-22 9:55 ` Thomas Gleixner
2018-11-22 9:45 ` Peter Zijlstra
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