Linus Torvalds just merged another set of pull requests to Git for the in-development Linux 6.19 kernel. With the latest round of merges, there are two separate AMD changes worth highlighting.
First up, the early preparations for AMD Zen 6 continues. On the RAS (Reliability, Availability and Serviceability) front, the RAS core merge adds support for two new Machine Check Architecture (MCA) bank bits to be found with AMD Zen 6 processors. These new bits denote whether the error address logged is a system physical address. If it’s a system physical address, further translation needs to be done before error recovery can be completed. Not exactly exciting for end-users but goes along with the early upbringing of Zen 6 platform support such as for the next-gen EPYC “Venice” server processors that are sure to see a lot of Linux action.
The other AMD change merged today for Linux 6.19 is a bit more exciting and that’s the x86/cache pull finally landing support for AMD Smart Data Cache Injection (SDCI). Smart Data Cache Injection is supported by AMD EPYC 9005 “Turin” CPUs and newer and is an exciting feature for modern servers.
Smart Data Cache Injection allows for data to be inserted from the I/O devices into the L3 cache directly, bypassing the system memory (DRAM) and in turn saving bandwidth. With the Linux resource control “resctrl” interface allows controlling the amount of L3 that can be used for data injection.
Smart Data Cache Injection as mentioned can be found with existing AMD Zen 5 servers. Besides the changes merged now, SDCI also depends upon device driver integration for leveraging this functionality and so far there’s been patches floated for use with select network drivers. SDCI patches for Linux have been under review for more than one year — they were first talked about on Phoronix back in August 2024 before even being announced by AMD as part of the 5th Gen EPYC launch. It also took longer to land as AMD first needed to bring-up PCIe Transaction Processing Hint (TPH) support to the Linux kernel as a prerequisite for SDCI.
The AMD Zen 6 RAS preparations and AMD SDCI are just the very latest Linux 6.19 features to talk about… More work is still to land over the next two weeks, including additional AMD client and server functionality.
