linux-kernel - Re: [RFC 05/10] x86/speculation: Add basic IBRS support infrastructure

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Date:   Sun, 21 Jan 2018 15:25:38 -0000
From:   "David Woodhouse" <dwmw2@...radead.org>
To:     "Thomas Gleixner" <tglx@...utronix.de>
Cc:     "KarimAllah Ahmed" <karahmed@...zon.de>,
        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>,
        "David Woodhouse" <dwmw@...zon.co.uk>,
        "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>,
        "Tim Chen" <tim.c.chen@...ux.intel.com>,
        "Tom Lendacky" <thomas.lendacky@....com>, kvm@...r.kernel.org,
        x86@...nel.org
Subject: Re: [RFC 05/10] x86/speculation: Add basic IBRS support
 infrastructure


> On Sat, 20 Jan 2018, KarimAllah Ahmed wrote:
>> From: David Woodhouse <dwmw@...zon.co.uk>
>>
>> Not functional yet; just add the handling for it in the Spectre v2
>> mitigation selection, and the X86_FEATURE_IBRS flag which will control
>> the code to be added in later patches.
>>
>> Also take the #ifdef CONFIG_RETPOLINE from around the RSB-stuffing; IBRS
>> mode will want that too.
>>
>> For now we are auto-selecting IBRS on Skylake. We will probably end up
>> changing that but for now let's default to the safest option.
>>
>> XX: Do we want a microcode blacklist?
>
> Oh yes, we want a microcode blacklist. Ideally we refuse to load the
> affected microcode in the first place and if its already loaded then at
> least avoid to use the borked features.
>
> PR texts promising that Intel is committed to transparency in this matter
> are not sufficient. Intel, please provide the facts, i.e. a proper list of
> micro codes and affected SKUs, ASAP.

Perhaps we could start with the list already published by VMware at
https://kb.vmware.com/s/article/52345


-- 
dwmw2