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

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Date:	Thu, 01 Aug 2013 06:42:14 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Takao Indoh <indou.takao@...fujitsu.com>
Cc:	bhelgaas@...gle.com, 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, hbabu@...ibm.com, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Reset PCIe devices to stop ongoing DMA

On Thu, 2013-08-01 at 15:34 +0900, Takao Indoh wrote:
> (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?

I'll post a non-RFC version today, I've made a couple cleanups, tuned
the delays and rolled in the AER version of secondary bus reset.
Thanks,

Alex


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