From: Paolo Bonzini <pbonzini@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Ashok Raj <ashok.raj@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg KH <gregkh@linuxfoundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Asit Mallick <asit.k.mallick@intel.com>,
Jason Baron <jbaron@akamai.com>
Subject: Re: [PATCH 23/35] x86/speculation: Add basic speculation control code
Date: Thu, 18 Jan 2018 18:12:36 +0100 [thread overview]
Message-ID: <a0308ee6-959a-0a78-9205-8de0a60948ac@redhat.com> (raw)
In-Reply-To: <73a5735a-6a5b-0e0f-1f0b-e7cd955880d2@intel.com>
On 18/01/2018 18:08, Dave Hansen wrote:
> On 01/18/2018 08:37 AM, Josh Poimboeuf wrote:
>>>
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -3932,6 +3932,7 @@
>>> retpoline - replace indirect branches
>>> retpoline,generic - google's original retpoline
>>> retpoline,amd - AMD-specific minimal thunk
>>> + ibrs - Intel: Indirect Branch Restricted Speculation
>> Are there plans to add spectre_v2=ibrs_always to prevent SMT-based
>> attacks?
>
> What does "ibrs_always" mean to you?
>
> There is a second bit in the MSR (STIBP) that is intended to keep
> hyperthreads from influencing each-other. That is behavior is implicit
> when IBRS is enabled.
Yeah, I think we should have a mode to always leave that enabled, or
always set IBRS=1.
> I think ibrs_always *should* probably be kept to refer to the future
> CPUs that can safely leave IBRS enabled all the time.
Is that "safely" or "without throwing performance down the drain"?
Does "always IBRS=1" *hinder* the mitigation on existing processor, as
long as you reset IBRS=1 on kernel entry and vmexit? Or is it just slow?
Paolo
next prev parent reply other threads:[~2018-01-18 17:12 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-18 13:48 [PATCH 00/35] jump_label, objtool, IBRS and IBPB Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 01/35] jump_label: Add branch hints to static_branch_{un,}likely() Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 02/35] sched: Optimize ttwu_stat() Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 03/35] x86: Reindent _static_cpu_has Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 04/35] x86: Update _static_cpu_has to use all named variables Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 05/35] x86: Add a type field to alt_instr Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 06/35] objtool: Implement base jump_assert support Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 07/35] x86: Annotate static_cpu_has alternative Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 08/35] objtool: Implement jump_assert for _static_cpu_has() Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 09/35] objtool: Introduce special_type Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 10/35] x86/jump_label: Implement arch_static_assert() Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 11/35] objtool: Add retpoline validation Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 12/35] x86/paravirt: Annotate indirect calls Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 13/35] x86,nospec: Annotate indirect calls/jumps Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 14/35] x86: Annotate indirect jump in head_64.S Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 15/35] objtool: More complex static jump implementation Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 16/35] objtool: Use existing global variables for options Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 17/35] objtool: Even more complex static block checks Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 18/35] objtool: Another static block fail Peter Zijlstra, Peter Zijlstra
2018-01-19 16:42 ` Peter Zijlstra
2018-01-29 18:01 ` Josh Poimboeuf
2018-01-29 18:24 ` Peter Zijlstra
2018-01-18 13:48 ` [PATCH 19/35] objtool: Skip static assert when KCOV/KASAN Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 20/35] x86: Force asm-goto Peter Zijlstra, Peter Zijlstra
2018-01-18 16:25 ` David Woodhouse
2018-01-18 13:48 ` [PATCH 21/35] x86: Remove FAST_FEATURE_TESTS Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 22/35] x86/cpufeatures: Detect Speculation control feature Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 23/35] x86/speculation: Add basic speculation control code Peter Zijlstra, Peter Zijlstra
2018-01-18 16:37 ` Josh Poimboeuf
2018-01-18 17:08 ` Dave Hansen
2018-01-18 17:12 ` Paolo Bonzini [this message]
2018-01-18 18:24 ` Josh Poimboeuf
2018-01-18 19:08 ` Andrea Arcangeli
2018-01-18 23:25 ` Andy Lutomirski
2018-01-18 23:35 ` Andrew Cooper
2018-01-19 1:41 ` Andrea Arcangeli
2018-01-19 4:10 ` Andy Lutomirski
2018-01-19 4:15 ` Van De Ven, Arjan
2018-01-19 15:47 ` Andrea Arcangeli
2018-01-18 13:48 ` [PATCH 24/35] x86/msr: Move native_*msr macros out of microcode.h Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 25/35] x86/speculation: Add inlines to control Indirect Branch Speculation Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 26/35] x86/enter: Create macros to stop/restart " Peter Zijlstra, Peter Zijlstra
2018-01-18 19:44 ` Tim Chen
2018-01-18 13:48 ` [PATCH 27/35] x86/enter: Use IBRS on syscall and interrupts Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 28/35] x86/idle: Control Indirect Branch Speculation in idle Peter Zijlstra, Peter Zijlstra
2018-01-18 19:52 ` Andrew Cooper
2018-01-18 13:48 ` [PATCH 29/35] x86/speculation: Add IPBP support Peter Zijlstra, Peter Zijlstra
2018-01-18 16:22 ` Josh Poimboeuf
2018-01-18 18:31 ` Borislav Petkov
2018-01-18 18:35 ` Josh Poimboeuf
2018-01-18 18:46 ` Borislav Petkov
2018-01-18 13:48 ` [PATCH 30/35] x86/speculation: Use Indirect Branch Prediction Barrier in context switch Peter Zijlstra, Peter Zijlstra
2018-01-19 0:38 ` Tim Chen
2018-01-19 4:03 ` Kevin Easton
2018-01-19 20:26 ` Tim Chen
2018-01-18 13:48 ` [PATCH 31/35] x86/ibrs: Add new helper macros to save/restore MSR_IA32_SPEC_CTRL Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 32/35] x86/vmx: Direct access to MSR_IA32_SPEC_CTRL Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 33/35] x86/svm: " Peter Zijlstra, Peter Zijlstra
2018-01-18 13:48 ` [PATCH 34/35] x86/kvm: Add IBPB support Peter Zijlstra, Peter Zijlstra
2018-01-18 15:32 ` Paolo Bonzini
2018-01-19 15:25 ` Paolo Bonzini
2018-01-19 16:08 ` David Woodhouse
2018-01-19 16:27 ` Andy Lutomirski
2018-01-19 16:48 ` Paolo Bonzini
2018-01-18 13:48 ` [PATCH 35/35] x86/nospec: Add static assertions Peter Zijlstra, Peter Zijlstra
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