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    SubjectRe: [PATCH 00/16] kvm: arm64: Support for dynamic IPA size
    I can comment on one part here:

    On Thu, Feb 08, 2018 at 12:18:44PM +0100, Christoffer Dall wrote:
    > Wasn't this also the decision taken for IOMMU page table allocation, and
    > why was that the right approach for the IOMMU but not for KVM stage 2
    > page tables? Is there room for reuse of the IOMMU page table allocation
    > logic in KVM as well?

    There were a few reasons we did this for IOMMU page tables:

    * Ability to use different page size/VA bits/levels from the CPU
    * Ability to support different page table formats (e.g. short descriptor)
    * Ability to determine page table attributes at runtime
    * Requirement to map/unmap in atomic context
    * Ability to cope with non-coherent page table walkers
    * Ability to create both stage-1 and stage-2 mappings
    * Easier to hook in our own TLB invalidation routines
    * Support for lockless concurrent map/unmap within confines of the DMA API
    usage

    Will

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