Messages in this thread | | | Date | Tue, 7 Jun 2005 10:21:43 -0600 | From | Grant Grundler <> | Subject | Re: [RFC/PATCH] Kdump: Disabling PCI interrupts in capture kernel |
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On Tue, Jun 07, 2005 at 03:59:18AM -0600, Eric W. Biederman wrote: > > *lots* of PCI devices predate PCI2.3. Possibly even the majority. > > In general generic hardware bits for disabling DMA, disabling interrupts > and the like are all advisory. With the current architecture things > will work properly even if you don't manage to disable DMA (assuming > you don't reassign IOMMU entries at least).
ISTR, pSeries (IBM), some alpha, some sparc64, and parisc (64-bit) require use of the IOMMU for *any* DMA. ie IOMMU entries need to be programmed. Probably want to make a choice to ignore those arches for now or sort out how to deal with an IOMMU.
> Shared interrupts are an interesting case. The simplest solution I can > think of for a crash dump capture kernel is to periodically poll > the hardware, as if all interrupts are shared. At that level > I think we could get away with ignoring all hardware interrupt sources.
Yes, that's perfectly ok. We are no longer in a multitasking env.
> Does anyone know of a anything that would break by always polling > the hardware? I guess there could be a problem with drivers > that don't understand shared interrupts, are there enough of those > to be an issue.
PCI requires drivers support Shared IRQs. A few oddballs might be broken but I expect networking/mass storage drivers get this right.
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