Re: [Xen-devel] [RFC 12/19] xen/passthrough: iommu_deassign_device_dt: By default reassign device to nobody

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-07-03 at 13:07 +0100, Julien Grall wrote:
> >> If Xen reassigns the device to "nobody", it may receive some global/context
> >> fault because the transaction has failed (indeed the context has been
> >> marked invalid).
> > 
> > Can you describe here what happen in this case (I presume Xen tears down
> > the iommu to quiesce them somehow?)
> 
> The SMMU drivers will mark the different Context Bank, S2CR, SMR as
> invalid. If the device is attempt to access the memory then, we will
> receive an interrupt in Xen.
> 
> Actually it's only happen once, if the device is still enabled when the
> domain is shutdown.

My concern was with getting a storm of such interrupts after this point.
If it only happens once and any subsequent ones are damped by some means
then great.

Ian.


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