From: Tim Chen <tim.c.chen@linux.intel.com>
To: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>
Cc: "x86@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>,
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>
Subject: Re: [patch V2 18/28] x86/speculation: Prepare for per task indirect branch speculation control
Date: Tue, 27 Nov 2018 11:51:41 -0800 [thread overview]
Message-ID: <b2442439-a3ea-00f6-955f-f0c5d99ec401@linux.intel.com> (raw)
In-Reply-To: <7ec59a1a-4caf-24f6-3466-ee1d01594861@amd.com>
On 11/27/2018 09:25 AM, Lendacky, Thomas wrote:
>> --- 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);
>>
>> + /* Conditional STIBP enabled? */
>> + 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
>> @@ -406,6 +406,11 @@ static __always_inline void spec_ctrl_up
>> if (static_cpu_has(X86_FEATURE_SSBD))
>> msr |= ssbd_tif_to_spec_ctrl(tifn);
>
> I did some quick testing and found my original logic was flawed. Since
> spec_ctrl_update_msr() can now be called for STIBP, an additional check
> is needed to set the SSBD MSR bit.
>
> Both X86_FEATURE_VIRT_SSBD and X86_FEATURE_LS_CFG_SSBD cause
> X86_FEATURE_SSBD to be set. Before this patch, spec_ctrl_update_msr() was
> only called if X86_FEATURE_SSBD was set and one of the other SSBD features
> wasn't set. But now, STIBP can cause spec_ctrl_update_msr() to get called
> and cause the SSBD MSR bit to be set when it shouldn't (could result in
> a GP fault).
>
I think it will be cleaner just to fold the msr update into
__speculation_ctrl_update to fix this issue.
Something like this perhaps.
Thanks.
Tim
---
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 3f5e351..614ec51 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -398,25 +398,6 @@ static __always_inline void amd_set_ssb_virt_state(unsigned long tifn)
wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn));
}
-static __always_inline void spec_ctrl_update_msr(unsigned long tifn)
-{
- u64 msr = x86_spec_ctrl_base;
-
- /*
- * If X86_FEATURE_SSBD is not set, the SSBD bit is not to be
- * touched.
- */
- if (static_cpu_has(X86_FEATURE_SSBD))
- msr |= ssbd_tif_to_spec_ctrl(tifn);
-
- /* Only evaluate if conditional STIBP is enabled */
- if (IS_ENABLED(CONFIG_SMP) &&
- static_branch_unlikely(&switch_to_cond_stibp))
- msr |= stibp_tif_to_spec_ctrl(tifn);
-
- wrmsrl(MSR_IA32_SPEC_CTRL, msr);
-}
-
/*
* Update the MSRs managing speculation control, during context switch.
*
@@ -428,6 +409,7 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
{
unsigned long tif_diff = tifp ^ tifn;
bool updmsr = false;
+ u64 msr = x86_spec_ctrl_base;
/*
* If TIF_SSBD is different, select the proper mitigation
@@ -440,8 +422,10 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
amd_set_ssb_virt_state(tifn);
else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD))
amd_set_core_ssb_state(tifn);
- else if (static_cpu_has(X86_FEATURE_SSBD))
+ else if (static_cpu_has(X86_FEATURE_SSBD)) {
updmsr = true;
+ msr |= ssbd_tif_to_spec_ctrl(tifn);
+ }
}
/*
@@ -449,11 +433,13 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
* otherwise avoid the MSR write.
*/
if (IS_ENABLED(CONFIG_SMP) &&
- static_branch_unlikely(&switch_to_cond_stibp))
+ static_branch_unlikely(&switch_to_cond_stibp)) {
updmsr |= !!(tif_diff & _TIF_SPEC_IB);
+ msr |= stibp_tif_to_spec_ctrl(tifn);
+ }
if (updmsr)
- spec_ctrl_update_msr(tifn);
+ wrmsrl(MSR_IA32_SPEC_CTRL, msr);
}
void speculation_ctrl_update(unsigned long tif)
next prev parent reply other threads:[~2018-11-27 19:51 UTC|newest]
Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-25 18:33 [patch V2 00/28] x86/speculation: Remedy the STIBP/IBPB overhead Thomas Gleixner
2018-11-25 18:33 ` [patch V2 01/28] x86/speculation: Update the TIF_SSBD comment Thomas Gleixner
2018-11-28 14:20 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:27 ` [patch V2 01/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 02/28] x86/speculation: Clean up spectre_v2_parse_cmdline() Thomas Gleixner
2018-11-28 14:20 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:28 ` [patch V2 02/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 03/28] x86/speculation: Remove unnecessary ret variable in cpu_show_common() Thomas Gleixner
2018-11-28 14:21 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:28 ` [patch V2 03/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 04/28] x86/speculation: Reorganize cpu_show_common() Thomas Gleixner
2018-11-26 15:08 ` Borislav Petkov
2018-11-28 14:22 ` [tip:x86/pti] x86/speculation: Move STIPB/IBPB string conditionals out of cpu_show_common() tip-bot for Tim Chen
2018-11-29 14:29 ` [patch V2 04/28] x86/speculation: Reorganize cpu_show_common() Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 05/28] x86/speculation: Disable STIBP when enhanced IBRS is in use Thomas Gleixner
2018-11-28 14:22 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:35 ` [patch V2 05/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 06/28] x86/speculation: Rename SSBD update functions Thomas Gleixner
2018-11-26 15:24 ` Borislav Petkov
2018-11-28 14:23 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-29 14:37 ` [patch V2 06/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 07/28] x86/speculation: Reorganize speculation control MSRs update Thomas Gleixner
2018-11-26 15:47 ` Borislav Petkov
2018-11-28 14:23 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:41 ` [patch V2 07/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 08/28] sched/smt: Make sched_smt_present track topology Thomas Gleixner
2018-11-28 14:24 ` [tip:x86/pti] " tip-bot for Peter Zijlstra (Intel)
2018-11-29 14:42 ` [patch V2 08/28] " Konrad Rzeszutek Wilk
2018-11-29 14:50 ` Konrad Rzeszutek Wilk
2018-11-29 15:48 ` Peter Zijlstra
2018-11-25 18:33 ` [patch V2 09/28] x86/Kconfig: Select SCHED_SMT if SMP enabled Thomas Gleixner
2018-11-28 14:24 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-29 14:44 ` [patch V2 09/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 10/28] sched/smt: Expose sched_smt_present static key Thomas Gleixner
2018-11-28 14:25 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-29 14:44 ` [patch V2 10/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 11/28] x86/speculation: Rework SMT state change Thomas Gleixner
2018-11-28 14:26 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 12/28] x86/l1tf: Show actual SMT state Thomas Gleixner
2018-11-28 14:26 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 13/28] x86/speculation: Reorder the spec_v2 code Thomas Gleixner
2018-11-26 22:21 ` Borislav Petkov
2018-11-28 14:27 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 14/28] x86/speculation: Mark string arrays const correctly Thomas Gleixner
2018-11-28 14:27 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 15/28] x86/speculataion: Mark command line parser data __initdata Thomas Gleixner
2018-11-28 14:28 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 16/28] x86/speculation: Unify conditional spectre v2 print functions Thomas Gleixner
2018-11-28 14:29 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 17/28] x86/speculation: Add command line control for indirect branch speculation Thomas Gleixner
2018-11-28 14:29 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 18/28] x86/speculation: Prepare for per task indirect branch speculation control Thomas Gleixner
2018-11-27 17:25 ` Lendacky, Thomas
2018-11-27 19:51 ` Tim Chen [this message]
2018-11-28 9:39 ` Thomas Gleixner
2018-11-27 20:39 ` Thomas Gleixner
2018-11-27 20:42 ` Thomas Gleixner
2018-11-27 21:52 ` Lendacky, Thomas
2018-11-28 14:30 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-25 18:33 ` [patch V2 19/28] x86/process: Consolidate and simplify switch_to_xtra() code Thomas Gleixner
2018-11-26 18:30 ` Borislav Petkov
2018-11-28 14:30 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 20/28] x86/speculation: Avoid __switch_to_xtra() calls Thomas Gleixner
2018-11-28 14:31 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 21/28] x86/speculation: Prepare for conditional IBPB in switch_mm() Thomas Gleixner
2018-11-25 19:11 ` Thomas Gleixner
2018-11-25 20:53 ` Andi Kleen
2018-11-25 22:20 ` Thomas Gleixner
2018-11-25 23:04 ` Andy Lutomirski
2018-11-26 7:10 ` Thomas Gleixner
2018-11-26 13:36 ` Ingo Molnar
2018-11-26 3:07 ` Andi Kleen
2018-11-26 6:50 ` Thomas Gleixner
2018-11-28 14:31 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 22/28] ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS Thomas Gleixner
2018-11-28 14:32 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 23/28] x86/speculation: Split out TIF update Thomas Gleixner
2018-11-28 14:33 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 24/28] x86/speculation: Prepare arch_smt_update() for PRCTL mode Thomas Gleixner
2018-11-27 20:18 ` Lendacky, Thomas
2018-11-27 20:30 ` Thomas Gleixner
2018-11-27 21:20 ` Lendacky, Thomas
2018-11-28 14:34 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 25/28] x86/speculation: Add prctl() control for indirect branch speculation Thomas Gleixner
2018-11-28 14:34 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 26/28] x86/speculation: Enable prctl mode for spectre_v2_user Thomas Gleixner
2018-11-26 7:56 ` Dominik Brodowski
2018-11-28 14:35 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode Thomas Gleixner
2018-11-25 19:35 ` Randy Dunlap
2018-11-25 20:40 ` Linus Torvalds
2018-11-25 20:52 ` Jiri Kosina
2018-11-25 22:28 ` Thomas Gleixner
2018-11-26 13:30 ` Ingo Molnar
2018-11-26 20:48 ` Andrea Arcangeli
2018-11-26 20:58 ` Thomas Gleixner
2018-11-26 21:52 ` Lendacky, Thomas
2018-11-27 0:37 ` Tim Chen
2018-12-04 1:38 ` Tim Chen
2018-12-04 8:39 ` Jiri Kosina
2018-12-04 9:43 ` Arjan van de Ven
2018-12-04 9:46 ` Arjan van de Ven
2018-12-04 17:20 ` Linus Torvalds
2018-12-04 18:58 ` Tim Chen
2018-11-28 14:35 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-12-04 18:45 ` [patch V2 27/28] " Dave Hansen
2018-11-25 18:33 ` [patch V2 28/28] x86/speculation: Provide IBPB always command line options Thomas Gleixner
2018-11-28 14:36 ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-26 13:37 ` [patch V2 00/28] x86/speculation: Remedy the STIBP/IBPB overhead Ingo Molnar
2018-11-28 14:24 ` Thomas Gleixner
2018-11-29 19:02 ` Tim Chen
2018-12-10 23:43 ` Pavel Machek
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