linux-kernel - Re: [RFC 00/10] Speculation Control feature support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1516656469.9521.75.camel@infradead.org>
Date:   Mon, 22 Jan 2018 21:27:49 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        KarimAllah Ahmed <karahmed@...zon.de>,
        Mihai Carabas <mihai.carabas@...cle.com>
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Borislav Petkov <bp@...e.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Laura Abbott <labbott@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        x86@...nel.org
Subject: Re: [RFC 00/10] Speculation Control feature support

On Sun, 2018-01-21 at 09:02 -0500, Konrad Rzeszutek Wilk wrote:
> 
> 
> Depend on what we expose to the guest. That is if the guest is not suppose to have this exposed
> (say cpuid 27 bit is not exposed) then trap on the MSR (and give an #GP)?

I think for SPEC_CTRL we want to trap on the MSR anyway. Saving and
restoring is is *bizarrely* slow, apparently, even when it's zero.

I think we want to trap on the first access, and only then disable the
intercept and enable the save/restore. That way, sane guests that only
ever use retpoline and IBPB (which is write-only and doesn't need
saving) won't ever take the performance hit.

It's going to want this: https://patchwork.kernel.org/patch/10167667/

> Mihai (CC-ed) is working on this, when ready he can post an patch against this tree?

That'd be useful; thanks. The latest (including the bits on top that we
probably aren't going to submit, with saner bits near the beginning)
should always be at
http://git.infradead.org/linux-retpoline.git/shortlog/refs/heads/ibpb



Download attachment "smime.p7s" of type "application/x-pkcs7-signature" (5213 bytes)