From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1TBitA-0000Zu-Ae for kexec@lists.infradead.org; Wed, 12 Sep 2012 09:05:41 +0000 Received: from m1.gw.fujitsu.co.jp (unknown [10.0.50.71]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id 52F913EE0BB for ; Wed, 12 Sep 2012 18:05:35 +0900 (JST) Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 37C3C45DE5A for ; Wed, 12 Sep 2012 18:05:35 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1E94B45DE56 for ; Wed, 12 Sep 2012 18:05:35 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id EC4E01DB803C for ; Wed, 12 Sep 2012 18:05:34 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.240.81.134]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 9E69A1DB8051 for ; Wed, 12 Sep 2012 18:05:34 +0900 (JST) Message-ID: <50504F47.80909@jp.fujitsu.com> Date: Wed, 12 Sep 2012 18:00:55 +0900 From: Takao Indoh MIME-Version: 1.0 Subject: Re: [RFC][PATCH] Reset PCIe devices to address DMA problem on kdump with iommu References: <501BB4EF.7080909@jp.fujitsu.com> <20120803114643.GA28330@redhat.com> <501F4877.5050605@jp.fujitsu.com> <20120806203902.GH25559@redhat.com> <50473306.1070803@jp.fujitsu.com> <20120910143604.GB639@redhat.com> <504F1343.7030607@jp.fujitsu.com> <20120911144323.GF12039@redhat.com> In-Reply-To: <20120911144323.GF12039@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: vgoyal@redhat.com Cc: martin.wilck@ts.fujitsu.com, linux-pci@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, hbabu@us.ibm.com, ishii.hironobu@jp.fujitsu.com, bhelgaas@google.com (2012/09/11 23:43), Vivek Goyal wrote: > On Tue, Sep 11, 2012 at 07:32:35PM +0900, Takao Indoh wrote: > > [..] >> I'll post new patch which clears bus master bit and resets devices in >> second kernel. >> >> As to the boot parameter to enable this function, you suggested using >> reset_devices. I found that on a certain platform resetting devices >> caused PCIe error due to a hardware bug. Therefore I think we need >> new parameter apart from reset_devices to disable this function on >> such a machine. > > Can you explain a bit more how the error happens. I still don't think > that because of a bug in a platform somewhere we should be introducing > a separate command line parameter and not reuse the exisiting one. Also > you have not explained what's the bug and how a new parameter will > avoid the bug. The bug I mentioned is that ACS Violation occurs at PCIe switch when reading PCI configuration after device reset. I got information that this violation is caused by PCIe switch bug. The machine becomes fatal status by this error. The reason why I try to introduce new parameter is that I want to avoid regression by this patch. Let's say this patch was included in kernel and its reset function was enabled by reset_devices as you said. AFAIK reset_devices is always needed for kdump, so it means that devices are always reset at kdump boot time. It causes a regression that system always becomes abnormal status when we run kdump on the machine which has a bug I mentioned. To avoid this regression, I want to separate reset_devices from this reset function. Or how about this? - if user specify reset_devices, devices are reset by this patch, as you said. - To avoid a regression I said, add new parameter like "pci=noreset". If this parameter is specified, the reset function I add is disabled and we can avoid regression. Thanks, Takao Indoh _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec