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Message-ID: <18148.12140.21118.252581@cargo.ozlabs.ibm.com>
Date: Mon, 10 Sep 2007 03:37:48 +1000
From: Paul Mackerras <paulus@samba.org>
To: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>
Cc: akpm@osdl.org, Greg KH <greg@kroah.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       kristen.c.accardi@intel.com
Subject: Re: [RFC][Intel-IOMMU] Fix for IOMMU early crash
In-Reply-To: <20070908200523.GA16204@askeshav-devel.jf.intel.com>
References: <20070908200523.GA16204@askeshav-devel.jf.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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Keshavamurthy, Anil S writes:

> Subject: [RFC][Intel-IOMMU] Fix for IOMMU early crash
> 
> Populating pci_bus->sysdata way early in the pci discovery phase
> sets NON-NULL value to pci_dev->sysdata which breaks the assumption
> in the Intel IOMMU driver and crashes the system.
> 
> 
> In the drivers/pci/probe.c, pci_dev->sysdata gets a copy of
> its pci_bus->sysdata which is not required as
> the same can be obtained from pci_dev->bus->sysdata. More over 
> the left hand assignment of pci_dev->sysdata is never being used,

Wrong.  You needed to grep a bit more widely...

> so their is no point is setting 
> pci_dev->sysdata = pci_bus->sysdata;
> 
> This patch removes sysdata from pci_dev struct and creates a new
> field called sys_data which is exclusively used 
> by IOMMU driver to keep its per device context pointer.

This will break powerpc, because we use the pci_dev->sysdata field to
point to a firmware device tree node.  Please figure out another way
to solve your problem.

Paul.
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