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

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Date:   Sun, 21 Jan 2018 15:56:55 +0100
From:   Borislav Petkov <bp@...e.de>
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>,
        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 Sun, Jan 21, 2018 at 03:31:28PM +0100, Thomas Gleixner wrote:
> 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.

If we have to do blacklisting, then we need to blacklist microcode
revisions and fixed ones should be incremented. I.e., we need a way to
*detect* the faulty microcode revision at load time.

Also, blacklisting microcode for early loading will become an ugly dance
so I'd like to avoid it if possible.

Thus, it would be much much easier if dracut/initrd creation thing
already filters those blacklisted blobs by looking at the revision in
the header. Which is much easier.

Yeah, something like that.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--