From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from out01.mta.xmission.com ([166.70.13.231]) by bombadil.infradead.org with esmtp (Exim 4.69 #1 (Red Hat Linux)) id 1Ny9Dm-0006nU-GU for kexec@lists.infradead.org; Sat, 03 Apr 2010 19:41:31 +0000 Subject: Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash" References: <20100403012751.834020949@sous-sol.org> <20100403012820.229410717@sous-sol.org> <20100403174128.GQ24846@8bytes.org> <20100403191314.GR24846@8bytes.org> From: ebiederm@xmission.com (Eric W. Biederman) Date: Sat, 03 Apr 2010 12:41:21 -0700 In-Reply-To: <20100403191314.GR24846@8bytes.org> (Joerg Roedel's message of "Sat\, 3 Apr 2010 21\:13\:14 +0200") Message-ID: MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Joerg Roedel Cc: nhorman@redhat.com, nhorman@tuxdriver.com, Joerg Roedel , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Chris Wright , hbabu@us.ibm.com, iommu@lists.linux-foundation.org, vgoyal@redhat.com Joerg Roedel writes: > On Sat, Apr 03, 2010 at 10:49:09AM -0700, Eric W. Biederman wrote: >> Joerg Roedel writes: > >> > Another problem: This also breaks if the kdump kernel has no >> > iommu-support. >> >> Not a problem. We require a lot of things of the kdump kernel, >> and it is immediately apparent in a basic sanity test. > > Only if the sanity test is done on an iommu machine which I don't want > to rely on. That makes no sense. The requirements on the kdump kernel has always been that it somehow figure out to recover a machine that is in a random hardware state. That requires drivers for the hardware, that is critical to the machines operation. The easy test for sysadmins is to do: echo > /proc/sysrq-trigger Anyone who thinks the result from one piece of hardware applies to another is deluded. We have been down the path of doing lots of things in the crashing kernel with lkcd, in practice it was worthless in the event of real world crashes. kexec on panic isn't perfect but it at least is an architecture that works often enough to be usable. It does require testing to make certain the basic code paths don't regress, but even so it is a lot easier to maintain and keep useful than any alternative I know of. Eric _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec