Intel VT-d Scalable Mode Coming To Linux 4.21 - Makes Up Scalable I/O Virtualization

The IOMMU changes were sent in today for the Linux 4.21 kernel merge window. There are some AMD IOMMU improvements, new Qualcomm SMMUv2 IOMMU hardware support, NUMA-aware allocations in the IOMMU DMA code for some very slight performance benefits, and most notably is likely the scalable mode support within the Intel VT-d driver.

Of the New Year's Eve pull request for the IOMMU code, catching most of my interest is the new scalable mode support within the Intel VT-d driver. This is a new translation mode for VT-d revision 3.0 that is part of what Intel now offers as Scalable I/O Virtualization. Scalable IOV is designed to allow highly-scalable and high performance sharing of I/O hardware between VMs/containers/processes.

Details on Intel Scalable I/O Virtualization can be found from this PDF presentation from this year's LinuxCon event in China. The technical details can be found in the Intel spec. At least with Linux 4.21 now, the scalable mode bits from the VT-d side should be in place.