Support VFIO migration manual clear interface & vSMMUv3/pSMMUv3 2 stage VFIO integration & Support migration in SMMUv3 nested mode · Pull Request !175 · openEuler/qemu

This set of patch mainly includes three parts：
- Suport manual clear vfio dirty log interface
- vSMMUv3/pSMMUv3 2 stage VFIO integration
- Support migration in SMMUv3 nested mode
Some necessary optimizations and bugfixes are alse include.

1) Suport manual clear vfio dirty log interface
In the past, we clear dirty log immediately after sync dirty log to
userspace. This may cause redundant dirty handling if userspace
handles dirty log iteratively:

After vfio clears dirty log, new dirty log starts to generate. These
new dirty log will be reported to userspace even if they are generated
before userspace handles the same dirty page.

Since a new dirty log tracking method for vfio based on iommu hwdbm
has been introduced in the kernel and added a new capability named
VFIO_DIRTY_LOG_MANUAL_CLEAR, we can eliminate some redundant dirty
handling by supporting it.

2) vSMMUv3/pSMMUv3 2 stage VFIO integration
Up to now vSMMUv3 has not been integrated with VFIO. VFIO
integration requires to program the physical IOMMU consistently
with the guest mappings. However, as opposed to VTD, SMMUv3 has
no "Caching Mode" which allows easy trapping of guest mappings.
This means the vSMMUV3 cannot use the same VFIO integration as VTD.

However SMMUv3 has 2 translation stages. This was devised with
virtualization use case in mind where stage 1 is "owned" by the
guest whereas the host uses stage 2 for VM isolation.

This series sets up this nested translation stage. It only works
if there is one physical SMMUv3 used along with QEMU vSMMUv3 (in
other words, it does not work if there is a physical SMMUv2).

3) Support migration in SMMUv3 nested mode
Since the SMMUv3's nested translation stages has been introduced by Eric, we
need to pay attention to the migration of VFIO PCI devices in SMMUv3 nested
stage mode. At present, it is not yet supported in QEMU. There are two problems
in the existing framework.

First, the current way to get dirty pages is not applicable to nested stage
mode. Because of the "Caching Mode", VTD can map the RAM through the host
single stage (giova->hpa). "vfio_listener_log_sync" gets dirty pages by
transferring "giova" to the kernel for the RAM block section of mapped MMIO
region. In nested stage mode, we setup the stage 2 (gpa->hpa) and the stage 1
(giova->gpa) separately. So it is inapplicable to get dirty pages by the
current way in nested stage mode.

Second, it also need to pass stage 1 configurations to the destination host
after the migration. In Eric's patch, it passes the stage 1 configuration to
the host on each STE update for the devices set the PASID PciOps. The
configuration will be applied at physical level. But the data of physical
level will not be sent to the destination host. So we have to pass stage 1
configurations to the destination host after the migration.

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