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

From: Alex Williamson
Date: Thu Aug 01 2013 - 08:42:57 EST

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@xxxxxxxxxxxxxx> 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.


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