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Date: Sun, 9 Sep 2007 20:51:40 +0300 From: Muli Ben-Yehuda <muli@...ibm.com> To: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com> Cc: akpm@...l.org, Greg KH <greg@...ah.com>, Linux Kernel <linux-kernel@...r.kernel.org>, kristen.c.accardi@...el.com Subject: Re: [RFC][Intel-IOMMU] Fix for IOMMU early crash On Mon, Sep 10, 2007 at 08:43:59AM -0700, Keshavamurthy, Anil S wrote: > On Sun, Sep 09, 2007 at 02:16:19PM +0300, Muli Ben-Yehuda wrote: > > On Sat, Sep 08, 2007 at 01:05:24PM -0700, Keshavamurthy, Anil S wrote: > > > > > Subject: [RFC][Intel-IOMMU] Fix for IOMMU early crash > > > > This patch feels like a huge hack. See below. > > You seem to be jumping to conclusion without going in detail. The > pci_dev struct contains pointer to sysdata, which in turn points to > the copy of its parent's bus sysdata. So technically speaking we > can eliminate sysdata pointer from pci_dev struct which is what one > portion of this patch does. ... provided nothing relies on this relationship or the existence of the pci_dev's sysdata. Have you audited every architecture's use of the sysdata pointers? > > > 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. > > > > Hmpf, why is this needed? with the pci_sysdata work that recently went > > into mainline we have a void *iommu member in pci_sysdata which should > > be all that's needed. Please elaborate if it's not enough for your > > needs. > I looked at your patch and it was not suitable because I need to > store iommu private pointer in pci_dev Could you elaborate on why you need this? I'm assuming it's for the per-device IOMMU page tables? > and not in the pci_bus. So I have added a new member sys_data in the > pci_dev struct. I can change the name from sys_dev to iomu_priv to > clear the confusion. Do let me know. Well, you should be able to just use the pci_dev's ->sysdata (that's what it's there for after all!) but you might need to make it point to a structure if it's shared, the same way we did with the bus's ->sysdata. I agree that just having it point to the bus's ->sysdata is not very useful *but* there may be code in the kernel that relies on it (Calgary did until very recently...) so it would have to be audited first. Cheers, Muli - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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