On Wed, Sep 11, 2024 at 06:12:21AM +0000, Tian, Kevin wrote: > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > Sent: Wednesday, August 28, 2024 1:00 AM > > > [...] > > On a multi-IOMMU system, the VIOMMU object can be instanced to the > > number > > of vIOMMUs in a guest VM, while holding the same parent HWPT to share > > the > > Is there restriction that multiple vIOMMU objects can be only created > on a multi-IOMMU system? I think it should be generally restricted to the number of pIOMMUs, although likely (not 100% sure) we could do multiple vIOMMUs on a single-pIOMMU system. Any reason for doing that? > > stage-2 IO pagetable. Each VIOMMU then just need to only allocate its own > > VMID to attach the shared stage-2 IO pagetable to the physical IOMMU: > > this reads like 'VMID' is a virtual ID allocated by vIOMMU. But from the > entire context it actually means the physical 'VMID' allocated on the > associated physical IOMMU, correct? Quoting Jason's narratives, a VMID is a "Security namespace for guest owned ID". The allocation, using SMMU as an example, should be a part of vIOMMU instance allocation in the host SMMU driver. Then, this VMID will be used to mark the cache tags. So, it is still a software allocated ID, while HW would use it too. Thanks Nicolin
