[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <1516993916.30244.284.camel@infradead.org>
Date: Fri, 26 Jan 2018 19:11:56 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Andi Kleen <ak@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Dave Hansen <dave.hansen@...el.com>,
Liran Alon <liran.alon@...cle.com>,
Laura Abbott <labbott@...hat.com>,
Andrew Lutomirski <luto@...nel.org>,
Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
Borislav Petkov <bp@...e.de>,
"Mallick, Asit K" <asit.k.mallick@...el.com>,
Radim Krčmář <rkrcmar@...hat.com>,
KarimAllah Ahmed <karahmed@...zon.de>,
Peter Anvin <hpa@...or.com>,
Jun Nakajima <jun.nakajima@...el.com>,
Ingo Molnar <mingo@...hat.com>,
the arch/x86 maintainers <x86@...nel.org>,
Ashok Raj <ashok.raj@...el.com>,
"Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Arjan van de Ven <arjan@...ux.intel.com>,
Tom Lendacky <thomas.lendacky@....com>,
Dan Williams <dan.j.williams@...el.com>,
Joerg Roedel <joro@...tes.org>,
Andrea Arcangeli <aarcange@...hat.com>,
KVM list <kvm@...r.kernel.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict
Indirect Branch Speculation
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.
Download attachment "smime.p7s" of type "application/x-pkcs7-signature" (5213 bytes)
Powered by blists - more mailing lists