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

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Message-ID: <20190405153048.knaizips2n27fwtx@treble>
Date:   Fri, 5 Apr 2019 10:30:48 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Borislav Petkov <bp@...en8.de>, 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 Fri, Apr 05, 2019 at 08:18:09AM -0700, Randy Dunlap wrote:
> 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

Ah, I didn't realize I was conforming to a standard.  I will update the
other arch strings as well.  Thanks.

-- 
Josh