Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 30 Jan 2018 14:11:22 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     David Woodhouse <dwmw2@infradead.org>, arjan@linux.intel.com,
        karahmed@amazon.de, x86@kernel.org, linux-kernel@vger.kernel.org,
        tim.c.chen@linux.intel.com, peterz@infradead.org,
        pbonzini@redhat.com, ak@linux.intel.com,
        torvalds@linux-foundation.org, gregkh@linux-foundation.org
Subject: Re: [PATCH] x86/cpuid: Fix up "virtual" IBRS/IBPB/STIBP feature bits
 on Intel
Message-ID: <20180130131122.s3bs6lbs43go73gj@pd.tnic>
References: <1517269773-16750-1-git-send-email-dwmw@amazon.co.uk>
 <20180130105814.m5zd43dyx2o2ius2@pd.tnic>
 <1517310230.18619.86.camel@infradead.org>
 <20180130111848.zjv2dngfzcz35lyt@pd.tnic>
 <1517311693.18619.102.camel@infradead.org>
 <alpine.DEB.2.20.1801301235500.1797@nanos>
 <1517314193.18619.115.camel@infradead.org>
 <alpine.DEB.2.20.1801301349140.1797@nanos>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.20.1801301349140.1797@nanos>
User-Agent: NeoMutt/20170609 (1.8.3)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jan 30, 2018 at 01:57:21PM +0100, Thomas Gleixner wrote:
> So much for the theory. That's not going to work. If the boot cpu has the
> feature then the alternatives will have been applied. So even if the flag
> mismatch can be observed when a secondary CPU comes up the outcome will be
> access to a non existing MSR and #GP.

Yes, with mismatched microcode we're f*cked.

So my question is: is there such microcode out there or is this
something theoretical which we want to address?

(.. and adressing this will be ugly, no matter what.)

And if I were able to wish, I'd like to blacklist that microcode in
dracut so that it doesn't come anywhere near my system.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.