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Re: [Xen-devel] [PATCH 5/25] Xen/doc: Add Xen virtual IOMMU doc


On 06/07/17 07:20, Lan Tianyu wrote:
On 2017年07月05日 21:25, Julien Grall wrote:
Furthermore, on ARM we would be able to create the vIOMMU but it would
be unusable. Indeed, IOMMU are only used to protect devices. But you
don't see any way to say "This device is protected by the IOMMU". Did I
miss anything?

The "device protection" you mentioned is DMA protection, right?. It's
one of IOMMU capabilities. IOMMU also provides interrupt remapping and
SVM(Shared virtual memory). I see ARM side also is pushing SVM feature
in KVM maillist for native support. Finally, it needs to support SVM in
VM and so virtual IOMMU is necessary regardless of full-virtualized or


I don't think SVM is strictly necessary to do DMA protection in the guest. Not all IOMMUs on ARM are able to use this feature but you may still want to allow the guest using the IOMMU. Did I miss anything?


Julien Grall

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