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Re: [Xen-devel] [PATCH v3 18/24] xen/passthrough: iommu_deassign_device_dt: By default reassign device to nobody

On 20/02/2015 17:04, Ian Campbell wrote:
On Tue, 2015-01-13 at 14:25 +0000, Julien Grall wrote:
Currently, when the device is deassigned from a domain, we directly reassign
to DOM0.

As the device may not have been correctly reset, this may lead to corruption or
expose some part of DOM0 memory. Also, we may have no way to reset some
platform devices.

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). Unfortunately there is no simple way to quiesce a buggy
hardware. I think we could live with that for a first version of platform
device passthrough.

DOM0 will have to issue an hypercall to assign the device to itself if it
wants to use it.

Does this behaviour differ from x86? If so then it is worth calling that
out explicitly (even if not, good to know I think!)

What do you mean by "calling that out explicitly"?


Julien Grall

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