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There is a lot coming for AMD processors with the Linux 6.18 kernel. Of the early pull requests submitted in advance of the planned Linux 6.17 kernel release later today, there are a number of changes already lined up with some exciting AMD CPU feature additions for the next kernel version. These AMD changes for Linux 6.18 are all the more important with that kernel expected to become this year's Long Term Support (LTS) kernel version.
First up, the EDAC pull request was already submitted in advance of the Linux 6.18 merge window. Notable here are some new Family 26 (0x1a) additions to the AMD64 EDAC driver.
The AMD64 Error Detection And Correction "EDAC" driver for Family 26 models 0xc0 to 0xc7 and 0x50 to 0x57 are now supported. These new IDs are likely for AMD EPYC Zen 6 "Venice" processors. The patch confirms those models support 16 channel memory compared to 12 channels with current generation AMD EPYC processors. So the next-gen EPYC processors should now have EDAC support with Linux 6.18 and the first to support 16 channel RAM.
The same patch also adds models 0x90 to 0x9f and 0xa0 to 0xaf to Family 26 for the AMD64 EDAC driver. Those models meanwhile max out with eight memory channels. With only eight channel support, perhaps these models are for the AMD EPYC 8004 "Siena" successor? EPYC 8004 supports six channel memory and we haven't heard much yet about AMD EPYC 8005 series but short of being for some new Threadripper PRO parts, that would be my guess for those eight channel Zen 5/Zen 6 parts.
The x86/cpu pull request for Linux 6.18 meanwhile cleans up and corrects AMD CPU topology detection. With the x86/microcode pull request from AMD's Borislav Petkov are new microcode loader additions to help in debugging CPU microcode issues.
With the x86/cache pull request for Linux 6.18 is support on AMD EPYC processors for assigning QOS bandwidth counters to resources. This is about the AMD Assignable Bandwidth Monitoring Counters "ABMC" support. This code has long been going through review but is now ready for the mainline kernel.
The x86/apic changes also are bringing some interesting work for AMD. There is now support for runtime firmware updates for the non-x86 parts of AMD platforms like for the security processor, modules, etc.
That x86 APIC pull also includes Secure AVIC support for better security and performance in helping Secure Encryption Virtualization (SEV).
Meanwhile over on the Kernel-based Virtual Machine "KVM" side there is code now ready for SEV-SNP CipherText Hiding. This is an opt-in SEV-SNP feature to prevent unauthorized CPU accesses from reading the cipher text of SNP guest private memory. This can help prevent offline attacks against AMD VMs using SEV-SNP on EPYC processors.
Via this pull is also now enabling AVIC by default on Zen 4 CPUs and newer if x2AVIC is supported. Plus there is support for Secure TSC to prevent untrusted hosts from tampering with the guest's TSC frequency. That AMD Secure TSC support is another Linux kernel feature that's taken years to bake.
The Linux 6.18 merge window hasn't even officially begun yet but already there is quite a bit on the AMD processor side for this next kernel cycle. Stay tuned to Phoronix for more details as the two week Linux 6.18 merge window gets underway. Linux 6.18 stable meanwhile should be out in December.
