linux-kernel - Re: [patch RFC 5/5] x86/speculation: Add basic speculation control code

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]

Date:   Tue, 9 Jan 2018 18:02:53 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...uxfoundation.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>
Subject: Re: [patch RFC 5/5] x86/speculation: Add basic speculation control
 code

On 01/09/2018 05:06 PM, Thomas Gleixner wrote:
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -79,6 +79,7 @@ enum spectre_v2_mitigation_cmd {
>  	SPECTRE_V2_CMD_RETPOLINE,
>  	SPECTRE_V2_CMD_RETPOLINE_GENERIC,
>  	SPECTRE_V2_CMD_RETPOLINE_AMD,
> +	SPECTRE_V2_CMD_IBRS,
>  };

A few nits on this:

IBRS should not default on anywhere, which goes double when retpolines
are available.

I think I'd also prefer that we separate the IBRS and retpoline enabling
so that you can do both if you want.  They do nearly the same thing in
practice, but I can't convince myself that you never ever need IBRS once
retpolines are in place.