From: David Woodhouse <dwmw2@infradead.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Andi Kleen <ak@linux.intel.com>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Dave Hansen" <dave.hansen@intel.com>,
"Liran Alon" <liran.alon@oracle.com>,
"Laura Abbott" <labbott@redhat.com>,
"Andrew Lutomirski" <luto@kernel.org>,
"Janakarajan Natarajan" <Janakarajan.Natarajan@amd.com>,
"Borislav Petkov" <bp@suse.de>,
"Mallick, Asit K" <asit.k.mallick@intel.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"KarimAllah Ahmed" <karahmed@amazon.de>,
"Peter Anvin" <hpa@zytor.com>,
"Jun Nakajima" <jun.nakajima@intel.com>,
"Ingo Molnar" <mingo@redhat.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
"Ashok Raj" <ashok.raj@intel.com>,
"Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
"Tim Chen" <tim.c.chen@linux.intel.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Masami Hiramatsu" <mhiramat@kernel.org>,
"Arjan van de Ven" <arjan@linux.intel.com>,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Joerg Roedel" <joro@8bytes.org>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"KVM list" <kvm@vger.kernel.org>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation
Date: Fri, 26 Jan 2018 19:11:56 +0000 [thread overview]
Message-ID: <1516993916.30244.284.camel@infradead.org> (raw)
In-Reply-To: <20180126190257.GS14668@char.us.oracle.com>
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On Fri, 2018-01-26 at 14:02 -0500, Konrad Rzeszutek Wilk wrote:
>
> -ECONFUSED, see ==>
>
> Is this incorrect then?
> I see:
>
> 241 * Skylake era CPUs have a separate issue with *underflow* of the
> 242 * RSB, when they will predict 'ret' targets from the generic BTB.
> 243 * The proper mitigation for this is IBRS. If IBRS is not supported
> 244 * or deactivated in favour of retpolines the RSB fill on context
> 245 * switch is required.
> 246 */
No, that's correct (well, except that it's kind of written for a world
where Linus is going to let IBRS anywhere near his kernel, and could
survive being rephrased a little :)
The RSB-stuffing on context switch (or kernel entry) is one of a
*litany* of additional hacks we need on Skylake to make retpolines
safe.
We were adding the RSB-stuffing in this case *anyway* for !SMEP, so it
was trivial enough to add in the (|| Skylake) condition while we were
at it.
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next prev parent reply other threads:[~2018-01-26 19:11 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-26 2:11 [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation Liran Alon
2018-01-26 2:23 ` Dave Hansen
2018-01-26 9:11 ` David Woodhouse
2018-01-26 17:19 ` Linus Torvalds
2018-01-26 17:27 ` Borislav Petkov
2018-01-26 17:29 ` David Woodhouse
2018-01-26 17:31 ` David Woodhouse
2018-01-26 17:59 ` Andi Kleen
2018-01-26 18:11 ` David Woodhouse
2018-01-26 18:12 ` Arjan van de Ven
2018-01-26 18:26 ` David Woodhouse
2018-01-26 18:28 ` Van De Ven, Arjan
2018-01-26 18:43 ` David Woodhouse
2018-01-26 18:44 ` Van De Ven, Arjan
2018-01-26 18:53 ` David Woodhouse
2018-01-26 19:02 ` Konrad Rzeszutek Wilk
2018-01-26 19:11 ` Hansen, Dave
2018-01-27 13:42 ` Konrad Rzeszutek Wilk
2018-01-27 15:55 ` Dave Hansen
2018-01-26 19:11 ` David Woodhouse [this message]
2018-01-26 8:46 ` David Woodhouse
-- strict thread matches above, loose matches on Subject: below --
2018-01-26 2:50 Liran Alon
2018-01-26 2:55 ` Van De Ven, Arjan
2018-01-23 11:13 Liran Alon
2018-01-25 22:20 ` Dave Hansen
2018-01-22 22:15 Luke Kenneth Casson Leighton
2018-01-20 19:22 [RFC 00/10] Speculation Control feature support KarimAllah Ahmed
2018-01-20 19:23 ` [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation KarimAllah Ahmed
2018-01-21 19:14 ` Andy Lutomirski
2018-01-23 16:12 ` Tom Lendacky
2018-01-23 16:20 ` Woodhouse, David
2018-01-23 22:37 ` Tom Lendacky
2018-01-23 22:49 ` Andi Kleen
2018-01-23 23:14 ` Woodhouse, David
2018-01-23 23:22 ` Andi Kleen
2018-01-24 0:47 ` Tim Chen
2018-01-24 1:00 ` Andy Lutomirski
2018-01-24 1:22 ` David Woodhouse
2018-01-24 1:59 ` Van De Ven, Arjan
2018-01-24 3:25 ` Andy Lutomirski
2018-01-21 19:34 ` Linus Torvalds
2018-01-21 20:28 ` David Woodhouse
2018-01-21 21:35 ` Linus Torvalds
2018-01-21 22:00 ` David Woodhouse
2018-01-21 22:27 ` Linus Torvalds
2018-01-22 16:27 ` David Woodhouse
2018-01-23 7:29 ` Ingo Molnar
2018-01-23 7:53 ` Ingo Molnar
2018-01-23 9:27 ` Ingo Molnar
2018-01-23 9:37 ` David Woodhouse
2018-01-23 15:01 ` Dave Hansen
2018-01-23 9:30 ` David Woodhouse
2018-01-23 10:15 ` Ingo Molnar
2018-01-23 10:27 ` David Woodhouse
2018-01-23 10:44 ` Ingo Molnar
2018-01-23 10:57 ` David Woodhouse
2018-01-23 10:23 ` Ingo Molnar
2018-01-23 10:35 ` David Woodhouse
2018-02-04 18:43 ` Thomas Gleixner
2018-02-04 20:22 ` David Woodhouse
2018-02-06 9:14 ` David Woodhouse
2018-01-25 16:19 ` Mason
2018-01-25 17:16 ` Greg Kroah-Hartman
2018-01-29 11:59 ` Mason
2018-01-24 0:05 ` Andi Kleen
2018-01-23 20:16 ` Pavel Machek
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