From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from out02.mta.xmission.com ([166.70.13.232]) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1KW2BM-0006Uo-9j for kexec@lists.infradead.org; Thu, 21 Aug 2008 04:54:01 +0000 From: ebiederm@xmission.com (Eric W. Biederman) References: <1218138156.3361.386.camel@amd.troyhebe> <20080808014024.GB3911@redhat.com> <1218750773.3361.425.camel@amd.troyhebe> <20080815131359.GA10208@redhat.com> <1219081942.3361.436.camel@amd.troyhebe> <20080819134748.GC18972@redhat.com> Date: Wed, 20 Aug 2008 21:50:21 -0700 In-Reply-To: <20080819134748.GC18972@redhat.com> (Vivek Goyal's message of "Tue, 19 Aug 2008 09:47:48 -0400") Message-ID: MIME-Version: 1.0 Subject: Re: Trying to test my gart/iommu vmcore problem on RH 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: Vivek Goyal Cc: "Heber, Troy" , Kexec Mailing List , "Loftin, Terry" , Bob Montgomery Vivek Goyal writes: > Hi Bob, > > I am CCing this thread to kexec mailing list. It is good to discuss > the issue there to get the ideas. > > I will summarize the discussion so far. > > Bob is running into MCA in second kernel in kdump. Reason seems to be > that second kernel is trying to access the memory area marked as > GART aperture (by first kernel). Because GART aperture does not appear > as "reserved" or something else in /proc/iomem (in case kernel has > overridden the BIOS settings and has reserved a memory area), second > kernel thinks it is a valid RAM area and tries to dump it and runs into > issues. > > Few options Bob is considering are. > > - Update "e820" memory map to mark GART aperture as reserved, which will > be reflected in /proc/iomem also. Kexec-tools will not pass reserved > area to second kernel and it will not try to dump this area. > > > - Mark GART aperture as "GART aperture" in /proc/iomem and modify > kexec-tools to filter out this memroy from memory map passed to second > kernel. We should definitely reserve the resource, and it should definitely show up in /proc/iomem. > - Disable cpu side GART access in first kernel so that even if second > kernel tries to access it, it does not run into isseus. This is an interesting one. When I looked at this years ago I had the feeling that if we did this we could actually always use a 2G Aperture at a fixed address, and require going through the gart for all of lowmem. But that is a little more than we are talking about. Eric _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec