ARM Virtualization
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`AArch64 virtualization <https://developer.arm.com/documentation/100942/0100/aarch64-virtualization>`_

virtualization支撑：isolation, high availability, workload balancing, sandboxing

type 1: Hypervisor上跑Guest OS；例如xen

type 2: Host OS上跑hypervisor，hypervisor上跑Guest OS；例如virtualbox, vmware, kvm

VMID & ASID
==============

每个VM有它自己的ASID空间

VMID区分VM，ASID区分应用

System Memory Management Units (SMMUs)
===========================================

SMMU, DMA都是可以直接访问Physical Address的。。。

Guest OS -> VA -> MMU -> IPA -> MMU -> PA

DMA -> IPA -> SMMU ->  PA

virtualizing exceptions
==========================

GIC管所有Physical CPU, vCPU的中断