linux-kernel - Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

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Date:   Tue, 4 Dec 2018 10:43:17 +0100
From:   Arjan van de Ven <arjan@...ux.intel.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Lutomirski <luto@...nel.org>, thomas.lendacky@....com,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>, dave.hansen@...el.com,
        Casey Schaufler <casey.schaufler@...el.com>,
        "Mallick, Asit K" <asit.k.mallick@...el.com>, jcm@...hat.com,
        longman9394@...il.com, Greg KH <gregkh@...uxfoundation.org>,
        david.c.stewart@...el.com, Kees Cook <keescook@...omium.org>,
        Jason Brandt <jason.w.brandt@...el.com>
Subject: Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user
 space protection mode

>> On processors with enhanced IBRS support, we recommend setting IBRS to 1
>> and left set.
> 
> Then why doesn't CPU with EIBRS support acutally *default* to '1', with
> opt-out possibility for OS?

the BIOSes could indeed get this set up this way.

do you want to trust the bios to get it right?