Re: [Xen-devel] RE: Crashdump and IOMMU problems

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 23:11 +0100 on 11 May (1305155493), Kay, Allen M wrote:
> I believe Jan was involved with adding kexec support in iommu code.
> 
> As for systematic way to disable active DMA, isn't this similar to OS 
> shutdown case when all the drivers are unloaded?  Does kexec unload all of 
> the device drivers?  Once all the drivers are unloaded, there shouldn't be 
> any DMA transactions going on.
> 
> I don't know much about kexec flow but it sound like the high level flow is: 
> 1) dom0 kernel shutdown all of the device dirver and then 2) call 
> iommu_ops->suspend() or crash_shutdown() to disable all of the iommu hardware.
> 

In Xen we might have to kexec on crash without knowing even which VM is
driving the devices, so we can't do a clean unload.  It might be
worthwhile just walking the PCI busses disabling everything, though. 

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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