linux-kernel - Re: [PATCH 1/1] IOMMU: Save pci device id instead of pci

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Date:	Mon, 11 Nov 2013 08:55:04 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Joerg Roedel <joro@...tes.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"Vinod Koul" <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	<dmaengine@...r.kernel.org>,
	"open list:INTEL IOMMU (VT-d)" <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH 1/1] IOMMU: Save pci device id instead of pci_dev* pointer
 for DMAR devices

>> Hmmm, this is the thing I am most worried about. If we just only use
>> (pci_dev *) poninter in drhd->devices array as a identification. Change
>> (pci_dev *) pointer instead of pci device id segment:bus:devfn is safe.
>> Or, this is a wrong way to fix this issue. I don't know IOMMU driver much now,
>> so IOMMU guys any comments on this issue is welcome.
>>
>> If this is not safe, what about we both save pci device id and (pci_dev *) pointer
>> in drhd. So we can put pci_dev ref and set pci_dev * = NULL during device removed by bus notify, and
>> update (pci_dev *)pointer during device add.
> 
> I don't know the IOMMU drivers well either, but it seems like they
> rely on notifications of device addition and removal (see
> iommu_bus_notifier()).  It doesn't seem right for them to also use the
> generic PCI interfaces like pci_get_domain_bus_and_slot() because the
> IOMMU driver should already know what devices exist and their
> lifetimes.  It seems like confusion to mix the two.  But I don't have
> a concrete suggestion.

Maybe you are right~, I will try to rework the patch and resend soon.

Thanks!
Yijing.


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Thanks!
Yijing

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