From: David Woodhouse <dwmw2@infradead.org>
To: Andi Kleen <ak@linux.intel.com>,
pjt@google.com, linux-kernel@vger.kernel.org,
tim.c.chen@linux.intel.com, riel@redhat.com, jikos@kernel.org,
jpoimboe@redhat.com, luto@amacapital.net,
torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com,
peterz@infradead.org, dave.hansen@intel.com, mingo@kernel.org,
keescook@google.com, gregkh@linux-foundation.org,
arjan@linux.intel.com
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/pti] x86/retpoline: Fill RSB on context switch for affected CPUs
Date: Mon, 15 Jan 2018 11:13:16 +0100 [thread overview]
Message-ID: <1516011195.22147.132.camel@infradead.org> (raw)
In-Reply-To: <20180115000554.GA7844@tassilo.jf.intel.com>
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On Sun, 2018-01-14 at 16:05 -0800, Andi Kleen wrote:
> > + if ((!boot_cpu_has(X86_FEATURE_PTI) &&
> > + !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
> > + setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
> > + pr_info("Filling RSB on context switch\n");
> > + }
>
> Missing an option to turn this off.
Deliberately so. You can already boot with 'spectre_v2=off' to turn off
the mitigations. We are not intending to permit all the bullshit micro-
management of IBRS=3/IBPB=2/RSB=π nonsense.
If you choose retpoline, you get the RSB stuffing which is appropriate
along with that. With IBRS, you get the RSB stuffing which is
appropriate with that. You don't get command line or sysfs tunables to
mess it. You *do* have the source code, if you really want to make
changes. Don't.
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next prev parent reply other threads:[~2018-01-15 10:13 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 17:49 [PATCH] x86/retpoline: Fill RSB on context switch for affected CPUs David Woodhouse
2018-01-12 18:02 ` Andi Kleen
2018-01-12 18:23 ` David Woodhouse
2018-01-12 18:05 ` Andrew Cooper
2018-01-12 18:56 ` David Woodhouse
2018-01-12 23:41 ` Josh Poimboeuf
2018-01-14 11:39 ` Thomas Gleixner
2018-01-14 17:04 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-15 14:35 ` David Laight
2018-01-15 14:39 ` David Woodhouse
2018-01-15 14:42 ` Arjan van de Ven
2018-01-15 20:03 ` Kees Cook
2018-01-14 23:37 ` tip-bot for David Woodhouse
2018-01-15 0:05 ` Andi Kleen
2018-01-15 0:09 ` Andi Kleen
2018-01-15 10:13 ` David Woodhouse [this message]
2018-03-09 13:12 ` Maciej S. Szmigiero
2018-03-09 15:14 ` Andi Kleen
2018-03-09 15:33 ` Maciej S. Szmigiero
2018-03-09 15:38 ` Woodhouse, David
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