Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752349AbbGOOBn (ORCPT ); Wed, 15 Jul 2015 10:01:43 -0400 Received: from pearsoncomputing.net ([192.119.205.242]:4943 "EHLO mail.pearsoncomputing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751738AbbGOOBl (ORCPT ); Wed, 15 Jul 2015 10:01:41 -0400 X-Greylist: delayed 564 seconds by postgrey-1.27 at vger.kernel.org; Wed, 15 Jul 2015 10:01:41 EDT DKIM-Filter: OpenDKIM Filter v2.9.2 mail.pearsoncomputing.net 3D0116407C9 Message-ID: <55A6658D.6030802@raptorengineeringinc.com> Date: Wed, 15 Jul 2015 08:52:13 -0500 From: Timothy Pearson User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100922 Thunderbird/3.1.4 MIME-Version: 1.0 To: Sreekanth Reddy CC: Yinghai Lu , James Bottomley , martin.petersen@oracle.com, Linux-Scsi , "James E.J. Bottomley" , Sathya.Prakash@avagotech.com, Linux Kernel Mailing List , Christoph Hellwig , Bjorn Helgaas , "linux-pci@vger.kernel.org" Subject: Re: [PATCH v3] [SCSI] mpt2sas, mpt3sas: Abort initialization if no memory I/O resources detected References: <1436935796-28995-1-git-send-email-Sreekanth.Reddy@avagotech.com> <20150715062456.GB19028@dhcp-135-24-192-118.lsi.com> In-Reply-To: <20150715062456.GB19028@dhcp-135-24-192-118.lsi.com> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1744 Lines: 45 On 07/15/2015 01:24 AM, Sreekanth Reddy wrote: > On Tue, Jul 14, 2015 at 10:36:58PM -0700, Yinghai Lu wrote: >> On Tue, Jul 14, 2015 at 9:49 PM, Sreekanth Reddy >> wrote: >>> Driver crashes if the BIOS do not set up at least one >>> memory I/O resource. This failure can happen if the device is too >>> slow to respond during POST and is missed by the BIOS, but Linux >>> then detects the device later in the boot process. >> >> But pci subsystem should assign resources to those unassigned BAR. >> >> Do you mean even kernel can not assign resource to them? or it takes so long for >> mpt FW to get ready? > > This is not an issue from mpt FW. > > I have just kept the same description provide by Timothy in his > initial patch. > > But I observe that their may be chance of getting "unable to handle > kernel NULL pointer dereference" kernel panic if no Memory Resource > available in the PCI subsystem. So agreed to the Timothy proposal of > aborting the driver initialization if it doesn't detect any Memory > resource instead of whole system get into panic state. > >> >> Thanks >> >> Yinghai On some systems Linux is unable / unwilling to assign a BAR if the BIOS does not assign one at startup. I didn't look into the Linux allocator side of things in much detail, but it is quite possible that Linux is unaware the device only has partial resources assigned. -- Timothy Pearson Raptor Engineering +1 (415) 727-8645 http://www.raptorengineeringinc.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/