linux-kernel - Re: [PATCH v2] PCI: Reset PCIe devices to stop ongoing DMA

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Message-ID: <51FA015E.10901@jp.fujitsu.com>
Date:	Thu, 01 Aug 2013 15:34:06 +0900
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	bhelgaas@...gle.com
CC:	rjw@...k.pl, vgoyal@...hat.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org,
	kexec@...ts.infradead.org, ishii.hironobu@...fujitsu.com,
	ddutile@...hat.com, bill.sumner@...com, alex.williamson@...hat.com,
	hbabu@...ibm.com, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Reset PCIe devices to stop ongoing DMA

(2013/08/01 6:23), Rafael J. Wysocki wrote:
> On Wednesday, July 31, 2013 03:08:03 PM Bjorn Helgaas wrote:
>> [+cc Rafael, linux-acpi]
>>
>> On Tue, Jul 30, 2013 at 6:35 PM, Takao Indoh <indou.takao@...fujitsu.com> wrote:
>>
>>> On x86, currently IOMMU initialization run *after* PCI enumeration, but
>>> what you are talking about is that it should be changed so that x86
>>> IOMMU initialization is done *before* PCI enumeration like sparc, right?
>>
>> Yes.  I don't know whether or when that initialization order will ever
>> be changed, but I do think we should avoid building more
>> infrastructure that depends on the current order.
>>
>> Changing the order is a pretty big deal because it's a lot more than
>> just the IOMMU.  Basically I think we should be enumerating ACPI
>> devices, including the IOMMU, before PCI devices, but there's a lot of
>> legacy involved in that area.  Added Rafael in case he has any
>> thoughts.
> 
> Well, actually, I'm not really familiar with IOMMUs, sorry.
> 
> I do think that initializing IOMMU before PCI enumeration would be better,
> however.  At least if the ordering should be the same on all architectures,
> which I suppose is the case, that's the one I'd choose.

Ok guys. If x86 IOMMU maintainer also thinks changing order is
necessary, maybe I need to give up device reset in kdump kernel and
consider doing it in panic kernel.

Either way, I need bus reset interface to reset devices. Bjorn, could
you review the bus reset patches Alex posted yesterday?

Thanks,
Takao Indoh

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