linux-kernel - Re: [PATCH RFC 2/5] x86/speculation: Add support for 'cpu_spec

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Date:   Fri, 5 Apr 2019 08:18:09 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Kosina <jikos@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jon Masters <jcm@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-s390@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tyler Hicks <tyhicks@...onical.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH RFC 2/5] x86/speculation: Add support for
 'cpu_spec_mitigations=' cmdline options

On 4/5/19 6:57 AM, Borislav Petkov wrote:
> On Thu, Apr 04, 2019 at 11:44:12AM -0500, Josh Poimboeuf wrote:
>> Configure x86 runtime CPU speculation bug mitigations in accordance with
>> the 'cpu_spec_mitigations=' cmdline options.  This affects Meltdown,
>> Spectre v2, Speculative Store Bypass, and L1TF.
>>
>> The default behavior is unchanged.
>>
>> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
>> ---
>>  .../admin-guide/kernel-parameters.txt         | 15 +++++++++
>>  arch/x86/include/asm/processor.h              |  1 +
>>  arch/x86/kernel/cpu/bugs.c                    | 32 ++++++++++++++++---
>>  arch/x86/kvm/vmx/vmx.c                        |  2 ++
>>  arch/x86/mm/pti.c                             |  4 ++-
>>  5 files changed, 49 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index ac42e510bd6e..29dc03971630 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -2552,6 +2552,11 @@
>>  
>>  			off
>>  				Disable all speculative CPU mitigations.
>> +				Equivalent to: nopti [x86]
>> +					       nospectre_v2 [x86]
>> +					       spectre_v2_user=off [x86]
>> +					       spec_store_bypass_disable=off [x86]
>> +					       l1tf=off [x86]
>>  
>>  			auto (default)
>>  				Mitigate all speculative CPU vulnerabilities,
>> @@ -2560,12 +2565,22 @@
>>  				surprised by SMT getting disabled across kernel
>>  				upgrades, or who have other ways of avoiding
>>  				SMT-based attacks.
>> +				Equivalent to: pti=auto [x86]
>> +					       spectre_v2=auto [x86]
>> +					       spectre_v2_user=auto [x86]
>> +					       spec_store_bypass_disable=auto [x86]
>> +					       l1tf=flush [x86]
>>  
>>  			auto,nosmt
>>  				Mitigate all speculative CPU vulnerabilities,
>>  				disabling SMT if needed.  This is for users who
>>  				always want to be fully mitigated, even if it
>>  				means losing SMT.
>> +				Equivalent to: pti=auto [x86]
>> +					       spectre_v2=auto [x86]
>> +					       spectre_v2_user=auto [x86]
>> +					       spec_store_bypass_disable=auto [x86]
>> +					       l1tf=flush,nosmt [x86]
>>  
>>  	mminit_loglevel=
>>  			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
> 
> Yap, those sets look ok.

nit:  s/x86/X86/g
according to Documentation/admin-guide/kernel-parameters.rst


-- 
~Randy