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:   Mon, 19 Feb 2018 11:08:17 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     David Woodhouse <dwmw2@infradead.org>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Tim Chen <tim.c.chen@linux.intel.com>, hpa@zytor.com,
        tglx@linutronix.de, torvalds@linux-foundation.org,
        linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org,
        Borislav Petkov <bp@alien8.de>
Subject: Re: [tip:x86/pti] x86/speculation: Use IBRS if available before
 calling into firmware
Message-ID: <20180219100817.GO25201@hirez.programming.kicks-ass.net>
References: <1518362359-1005-1-git-send-email-dwmw@amazon.co.uk>
 <tip-670c3e8da87fa4046a55077b1409cf250865a203@git.kernel.org>
 <c77b3da9-136d-9988-119f-e94c86fd34a3@linux.intel.com>
 <1518808600.7876.49.camel@infradead.org>
 <66f94cb1-8160-56e0-680c-2e847ae05893@linux.intel.com>
 <20180217102616.vcwatxsgj2vunlew@gmail.com>
 <20180219092017.GN25201@hirez.programming.kicks-ass.net>
 <1519032552.7876.55.camel@infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <1519032552.7876.55.camel@infradead.org>
User-Agent: Mutt/1.9.2 (2017-12-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Feb 19, 2018 at 09:29:12AM +0000, David Woodhouse wrote:
> On Mon, 2018-02-19 at 10:20 +0100, Peter Zijlstra wrote:
> > 
> > I did not update or otherwise change packages while I was bisecting; the
> > machine is:
> > 
> > vendor_id?????? : GenuineIntel
> > cpu family????? : 6
> > model?????????? : 62
> > model name????? : Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz
> > stepping??????? : 4
> > microcode?????? : 0x428
> 
> That's IVX with a microcode that doesn't *have* IBRS/IBPB. I don't
> think there's a publicly available microcode that does; I assume you
> didn't have one and build it into your kernel for early loading, and
> thus you really weren't even using IBRS here? The code never even gets
> patched in?

I wasn't using IRBS afaik. I was bisceting tip/master before the
IBRS/firmware patches (not sure they're in now or not).

No fancy ucode setup, I think I have ucode image in the initrd, but that
would be same for all kernels.