linux-kernel - Re: [PATCH v3] [SCSI] mpt2sas, mpt3sas: Abort initialization if no memory I/O resources detected

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Message-ID: <55A6658D.6030802@raptorengineeringinc.com>
Date:	Wed, 15 Jul 2015 08:52:13 -0500
From:	Timothy Pearson <tpearson@...torengineeringinc.com>
To:	Sreekanth Reddy <sreekanth.reddy@...gotech.com>
CC:	Yinghai Lu <yinghai@...nel.org>, James Bottomley <jejb@...nel.org>,
	martin.petersen@...cle.com,
	Linux-Scsi <linux-scsi@...r.kernel.org>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	Sathya.Prakash@...gotech.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v3] [SCSI] mpt2sas, mpt3sas: Abort initialization if no
 memory I/O resources detected

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
>> <sreekanth.reddy@...gotech.com> 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
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