From owner-freebsd-stable@FreeBSD.ORG Fri Nov 25 20:38:17 2011 Return-Path: Delivered-To: stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 314DB106566B for ; Fri, 25 Nov 2011 20:38:17 +0000 (UTC) (envelope-from thomas.e.zander@googlemail.com) Received: from mail-ww0-f50.google.com (mail-ww0-f50.google.com [74.125.82.50]) by mx1.freebsd.org (Postfix) with ESMTP id B8AD88FC0A for ; Fri, 25 Nov 2011 20:38:16 +0000 (UTC) Received: by wwe5 with SMTP id 5so2636017wwe.31 for ; Fri, 25 Nov 2011 12:38:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=date:from:to:subject:message-id:mime-version:content-type :content-disposition:x-pgp-keyid:x-pgp-uri:x-pgp-fingerprint :x-mailer; bh=Oq8OnpoMbin/sFQuNuXfd3sjpZZDH7c07q+gvFlF8F0=; b=HwD5Ass13gk0b8E3JnEs1KbL+YF5p1dmg5inIR5s7OldmpOsbF0fmvC2Z2xtXPyMr0 xz5JNIo4QkQCsFXWxwbsu6V/5R14y7dU/pZ9/i0GpkR5o5mplklpLsKpz89oHfAl126I R3dQgDTTlRlL8+OY6TYnNl3l5vHPwVn2ZZfc0= Received: by 10.216.153.137 with SMTP id f9mr144520wek.4.1322252026245; Fri, 25 Nov 2011 12:13:46 -0800 (PST) Received: from localhost ([82.113.98.137]) by mx.google.com with ESMTPS id fg15sm5146086wbb.7.2011.11.25.12.13.40 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 25 Nov 2011 12:13:45 -0800 (PST) Date: Fri, 25 Nov 2011 21:13:31 +0100 From: Thomas Zander To: stable@freebsd.org Message-ID: <20111125201331.GA2193@marvin2011.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline X-PGP-KeyID: 0xC85996CD X-PGP-URI: http://pgpkeys.pca.dfn.de/pks/lookup?search=0xC85996CD X-PGP-Fingerprint: 4F59 75B4 4CE3 3B00 BC61 5400 8DD4 8929 C859 96CD X-Mailer: Marvin Mail (Build 1322247649) Cc: Subject: Sandy Bridge and MCA UNCOR PCC (problem + solution) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Nov 2011 20:38:17 -0000 List, here's a rant about a recent problem I had and the surprising solution. I recently had to investigate weird unexpected issues on a workstation. Relevant hardware: Asus P8B-WS, Xeon E3-1260L (Sandy Bride, Intel HD-2000 graphics) Since we don't have kms and friends in STABLE yet, and I can live without accelerated video for now, I am using the vesa driver on this machine. Initially, this had two major drawbacks: 1) 1280x1024 resolution utterly sucks on a 1680x1050 screen. 2) Reproducable unhandled MCA events (and subsequent kernel panics) like the following whenever I switch from X to console: panic: machine check trap ... MCA: CPU 6 UNCOR UNCOR UNCOR PCC PCC PCC internal error 2internal error 2PCC internal error 2 The kernel dump _always_ showed something like: current process = 11 (idle: cpu3) trap number = 28 #1 0xffffffff805db167 at panic+0x187 #2 0xffffffff808c6820 at trap_fatal+0x290 #3 0xffffffff808c6d3a at trap+0x10a #4 0xffffffff808ae894 at calltrap+0x8 #5 0xffffffff801f6b9a at acpi_cpu_idle+0x20a #6 0xffffffff806003af at sched_idletd+0x11f #7 0xffffffff805afe6f at fork_exit+0x11f #8 0xffffffff808aedde at fork_trampoline+0xe mcelog did not help decoding the MCA output and the "internal error2" message made me suspect that this CPU was maybe just broken. However, due to my utter inabilty of producing the slightest other problem with this machine (constantly heavy CPU + IO load) or any problem using other operating systems I derived the wild speculation that there might be something with the Sandy Bridge silicon which this exact sequence of actions on FreeBSD reliably could trigger. Long story short: I got the latest Bios from Asus for this Board. The changelog of course said absolutely nothing about fixing any known problem. Upon boot I entered the Bios settings and noticed that it apparently contained a microcode update. The changelog for microcode from Intel is of course non-existing. And since this boot there has not been a single problem with this machine. Vesa now works in 1680x1050 and switching from X to console and back does not trigger MCA events anymore. I like to believe that for the first time a microcode update from Intel fixed my specific problem. Anyway, now the story is on the list and for Google to find, in case anyone else has this problem as well. Best regards Riggs -- - Now the world has gone to bed | Now I lay me down to sleep - -- Darkness won't engulf my head | Try to count electric sheep -- --- I can see by infra-red | Sweet dream wishes you can keep --- ---- How I hate the night | How I hate the night ----