linux-kernel - Re: [PATCH v2 5/5] arm64/speculation: Support 'mitigations=' cmdline option

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Date:   Fri, 12 Apr 2019 16:34:47 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "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>,
        Steven Price <steven.price@....com>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v2 5/5] arm64/speculation: Support 'mitigations=' cmdline
 option

On 4/12/19 1:39 PM, Josh Poimboeuf wrote:
> Configure arm64 runtime CPU speculation bug mitigations in accordance
> with the 'mitigations=' cmdline option.  This affects Meltdown, Spectre
> v2, and Speculative Store Bypass.
> 
> The default behavior is unchanged.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> ---
> NOTE: This is based on top of Jeremy Linton's patches:
>       https://lkml.kernel.org/r/20190410231237.52506-1-jeremy.linton@arm.com
> 
>  Documentation/admin-guide/kernel-parameters.txt | 8 +++++---
>  arch/arm64/kernel/cpu_errata.c                  | 6 +++++-
>  arch/arm64/kernel/cpufeature.c                  | 8 +++++++-
>  3 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index e84a01d90e92..79bfc755defe 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2545,8 +2545,8 @@
>  			http://repo.or.cz/w/linux-2.6/mini2440.git
>  
>  	mitigations=
> -			[X86,PPC,S390] Control optional mitigations for CPU
> -			vulnerabilities.  This is a set of curated,
> +			[X86,PPC,S390,ARM64] Control optional mitigations for
> +			CPU vulnerabilities.  This is a set of curated,
>  			arch-independent options, each of which is an
>  			aggregation of existing arch-specific options.
>  
> @@ -2555,11 +2555,13 @@
>  				improves system performance, but it may also
>  				expose users to several CPU vulnerabilities.
>  				Equivalent to: nopti [X86,PPC]
> +					       kpti=0 [ARM64]
>  					       nospectre_v1 [PPC]
>  					       nobp=0 [S390]
> -					       nospectre_v2 [X86,PPC,S390]
> +					       nospectre_v2 [X86,PPC,S390,ARM64]
>  					       spectre_v2_user=off [X86]
>  					       spec_store_bypass_disable=off [X86,PPC]
> +					       ssbd=force-off [ARM64]
>  					       l1tf=off [X86]
>  
>  			auto (default)

Hi,
Do we need to add "ARM64" to Documentation/admin-guide/kernel-parameters.rst?


-- 
~Randy