Linux 5.19 Features: AMD SEV-SNP + Zen 4 Prep, Intel TDX + IFS, LoongArch, Big TCP, Apple M1 NVMe

With the Linux 5.19 merge window complete, here is my usual look at all of the interesting changes I've been watching for this next version of the Linux kernel. Linux 5.19 is quite a big summer time upgrade to this open-source kernel with many new and improved features coming for this kernel that will debut as stable in late July.

Linux 5.19 lands the initial but currently incomplete LoongArch CPU support, Zstd compression support for firmware files, long-awaited fixes to the NTFS3 kernel driver, continued AMD Zen 4 CPU preparations, more AMD RDNA3 GPU enablement work, continued Intel DG2/Alchemist discrete graphics enablement (including DG2 compute support!), proper file creation/birth time reporting for FAT32 file-systems Apple M1 NVMe controller support, support for Big TCP for dealing with TCP/IP stack overhead on 200Gbit and greater networks, Armv9 Scalable Matrix Extension support, Intel IFS, Intel TDX, and AMD SEV-SNP has also finally been merged. That's the short list, the rest of the article dives into more of the big changes coming with Linux 5.19.

Processors / Platforms:

- Intel In-Field Scan (IFS) is merged for facilitating CPU silicon tests prior to deployments in the data center or silicon testing over time for helping to catch any hardware problems not uncovered by ECC checks or other existing tests.

- LoongArch was merged as a new CPU port for the Linux kernel. However, as noted there isn't yet support for actually booting any LoongArch systems due to some drivers not being ready for mainlining yet.

- Support for the PolarBerry RISC-V FPGA board that makes use of the PolarFire SoC.

- Support for running 32-bit (RV32) binaries on RISC-V 64-bit (RV64).

- Completing the 12-year Arm multi-platform effort with the conversion finally of old ARMv4T/ARMv5 code for multi-platform kernel builds. Followed uo later in the merge window too with completed Arm multi-platform support for old Intel XScale/PXA hardware.

- The HPE GXP SoC is added with the HPE GXP SoC to be used for baseboard management controller (BMC) duties on forthcoming HPE servers.

- ARMv9 Scalable Matrix Extension support. Scalable Matrix Extension (SME) builds atop SVE/SVE2.

- The perf changes are heavy on the AMD side with Zen 4 IBS extensions, AMD PerfMonV2, and finally having AMD Zen 3 Branch Sampling (BRS).

- Removal of the old Renesas H8/300 CPU architecture. The architecture is old and has been unmaintained in the kernel for years, already being dropped once before from mainline.

- Removal of obsolete x86 a.out support.

- Many Intel power management and thermal updates -- including a fix to address hot Linux laptops draining the battery while trying to sleep.

- Easier clearing of CPUID features.

- Late microcode loading for x86/x86_64 disabled by default and will taint the kernel. Users are recommended to be early loading CPU microcode.

Virtualization:

- AMD SEV-SNP is finally mainlined for that update to Secure Encrypted Virtualization (SEV) introduced with AMD EPYC 7003 "Milan" processors.

- Intel Trust Domain Extensions (TDX) has been merged with the early code ready.

- Support for XSAVEC when running as a VM guest.

- Microsoft has trimmed Hyper-V guest boot times for big Azure VMs with many GPUs.

- Support for Linux's EFO to access VM secrets for confidential computing (CoCo) hypervisors such as with AMD SEV.

- KVM and Xen updates.

- A new virtual m68k machine target for virtualization usage that is based on Google's Goldfish and much more capable than existing Motorola 68000 emulation options.