On Thu, Nov 07, 2024 at 09:11:27PM +1100, Alexey Kardashevskiy wrote:
On 31/10/24 08:35, Nicolin Chen wrote:
Introduce a new IOMMUFD_OBJ_VDEVICE to represent a physical device (struct device) against a vIOMMU (struct iommufd_viommu) object in a VM.
This vDEVICE object (and its structure) holds all the infos and attributes in the VM, regarding the device related to the vIOMMU.
As an initial patch, add a per-vIOMMU virtual ID. This can be:
- Virtual StreamID on a nested ARM SMMUv3, an index to a Stream Table
- Virtual DeviceID on a nested AMD IOMMU, an index to a Device Table
- Virtual RID on a nested Intel VT-D IOMMU, an index to a Context Table
Potentially, this vDEVICE structure would hold some vData for Confidential Compute Architecture (CCA). Use this virtual ID to index an "vdevs" xarray that belongs to a vIOMMU object.
Add a new ioctl for vDEVICE allocations. Since a vDEVICE is a connection of a device object and an iommufd_viommu object, take two refcounts in the ioctl handler.
+/**
- struct iommu_vdevice_alloc - ioctl(IOMMU_VDEVICE_ALLOC)
- @size: sizeof(struct iommu_vdevice_alloc)
- @viommu_id: vIOMMU ID to associate with the virtual device
- @dev_id: The physical device to allocate a virtual instance on the vIOMMU
- @out_vdevice_id: Object handle for the vDevice. Pass to IOMMU_DESTORY
- @virt_id: Virtual device ID per vIOMMU, e.g. vSID of ARM SMMUv3, vDeviceID
of AMD IOMMU, and vRID of a nested Intel VT-d to a Context TableSo it is one vdevice per a passed through device (say, a network adapter), right?
Yes. It's per iommufd_device per iommufd_viommu.
I am asking as there are passed through devices and IOMMU devices, and (at least on AMD) IOMMUs look like PCI devices, both in hosts and guests. For example, from the above: "@dev_id: The physical device ..." - both a network card and IOMMU are physical, so dev_id is a NIC or IOMMU? I assume that шы a NIC (but it is a source of constant confusion).
In that case, dev_id is NIC. viommu_id is IOMMU.
First VMM should allocate a vIOMMU using the dev_id (NIC) to get a viommu_id, and then use this viommu_id and dev_id to allocate a vDEVICE.
It might sound duplicated in this case because this AMD IOMMU is exclusive for the NIC. But ARM/Intel can be shared among devices so they can allocate a vIOMMU with device1 and allocate vDEVICEs for device1, device2, device3, and so on.
Is there any plan to add guest device BDFn as well, or I can add one here for my TEE-IO exercise, if it is the right place? It is the same as vDeviceID for AMD but I am not sure about the others, hence the question. Thanks,
Generally speaking, adding vRID isn't a problem so long as there is a legit reason/usecase. That being said, if it is the same as the @virt_id for AMD, why not just pass via @virt_id v.s. adding a new vRID/vBDF field?
Thanks Nicolin