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.
grant
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