Re: [PATCH RFC 2/5] x86/speculation: Add support for 'cpu_spec_mitigations=' cmdline options

From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Randy Dunlap <rdunlap@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Kosina <jikos@kernel.org>, Waiman Long <longman@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Jon Masters <jcm@redhat.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	linuxppc-dev@lists.ozlabs.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux-s390@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Tyler Hicks <tyhicks@canonical.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH RFC 2/5] x86/speculation: Add support for 'cpu_spec_mitigations=' cmdline options
Date: Fri, 5 Apr 2019 10:30:48 -0500	[thread overview]
Message-ID: <20190405153048.knaizips2n27fwtx@treble> (raw)
In-Reply-To: <5ccc7515-33e6-b726-833e-9553ab0f4c6a@infradead.org>

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@redhat.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