From owner-freebsd-stable@FreeBSD.ORG Thu Feb 11 05:04:11 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 05F0D106568B for ; Thu, 11 Feb 2010 05:04:11 +0000 (UTC) (envelope-from alan.l.cox@gmail.com) Received: from mail-pz0-f179.google.com (mail-pz0-f179.google.com [209.85.222.179]) by mx1.freebsd.org (Postfix) with ESMTP id C30498FC0A for ; Thu, 11 Feb 2010 05:04:10 +0000 (UTC) Received: by pzk9 with SMTP id 9so1001256pzk.28 for ; Wed, 10 Feb 2010 21:04:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:reply-to:in-reply-to :references:date:message-id:subject:from:to:cc:content-type; bh=PBA1YrSv+Loz7rjzEBgbENqhwK6oV3BBKcMvJkQSV9o=; b=fPuK3TN86Bt8r7IuVjd9qlehS2pobKvKNiXuilKMXdLeLvmbVSwd9rSzuwLr2U0foC RmPpWTxErfEVkWr9pEgwkfYxSMnOa6zQ1B3eW+Hx1ZW/NEsnOWpTTj7Ka4GeMdNdH1D1 yDwBp75ntQiYDL182kHPyFwLjkhOZ2BXhc5Bw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:reply-to:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; b=it3ZLfr38/8QShsnu/ENcIRKyAgeu+8SsBUMwxzQmJroBHDMz+VaE+vKvyOf6D6Atu ZKZcd019DNNCksGOSn6l2xmUerIsN7IJrcgdqjwxWartHc0RMxWTPAXr7Ddiv/nRipTp 4FzOFIDcc+Iykhb4ARZvJkeiW395RS8DezpMs= MIME-Version: 1.0 Received: by 10.142.121.10 with SMTP id t10mr809513wfc.152.1265863028607; Wed, 10 Feb 2010 20:37:08 -0800 (PST) In-Reply-To: <20100210184623.GA78851@icarus.home.lan> References: <4B72D94A.8030509@icyb.net.ua> <4B72E93C.80102@icyb.net.ua> <9bbcef731002101003r203f5189xf139700a0d48afa0@mail.gmail.com> <4B72F67F.4000209@icyb.net.ua> <9bbcef731002101026k5007075cqf97fc80404ac3fa7@mail.gmail.com> <4B72FC55.2090508@icyb.net.ua> <9bbcef731002101038r1ac04141t505216816489376f@mail.gmail.com> <20100210184623.GA78851@icarus.home.lan> Date: Wed, 10 Feb 2010 22:37:08 -0600 Message-ID: From: Alan Cox To: Jeremy Chadwick Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-stable@freebsd.org Subject: Re: Strange problem with 8-stable, VMWare vSphere 4 & AMD CPUs (unexpected shutdowns) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: alc@freebsd.org List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Feb 2010 05:04:11 -0000 On Wed, Feb 10, 2010 at 12:46 PM, Jeremy Chadwick wrote: [snip] > > I read what Andriy wrote to mean that the way FreeBSD utilises 4MB TLB > on certain models of AMD processors is broken/quirky, and on those CPUs, > users should stick to vm.pmap.pg_ps_enabled="0" (loader.conf). > > No. He said, "We don't do anything that strays from specifications." So, he is not saying that FreeBSD is doing anything broken. Here is what I know. Several of us, myself included, have been able to reproduce either lockups or machine check exceptions when BOTH the machine check driver and superpages are enabled on AMD family 10h processors. There have been no reports of this problem on either Intel or earlier AMD processors. Moreover, there is no evidence of instability in AMD family 10h processors until the machine check driver is enabled. By default, FreeBSD 8.0 enables superpages but disables the machine check driver. So, running natively, i.e., without virtualization, you shouldn't experience a problem, unless you explicitly enable the machine check driver. However, running on top of a hypervisor, like vSphere 4, you might face a problem because the hypervisor might enable machine check exceptions, regardless of what the FreeBSD guest does. I really don't know whether vSphere 4 enables machine check exception or not. If it does, then either you disable the use of superpages in the FreeBSD guest, or you find a way to disable the machine check driver in the hypervisor. Both Andriy and I have reported this problem to people at AMD, but we haven't yet received AMD's analysis. These things take time. Regards, Alan