For such significant changes to the Linux kernel, getting all of the SEV-SNP code into the mainline Linux kernel has been slow going... Similar to Intel's Trust Domain Extensions (TDX) support also going through many rounds of revisions and a long time in the making. SEV-SNP premiered with the EPYC 7003 (Zen 3) server processors and continues to be supported with the latest EPYC 8004/9004 series processors.
On Saturday the 11th iteration of the SEV-SNP hypervisor support was sent out for review on the kernel mailing list. With this the patches for SEV-SNP initialization have been broken off into their own patch series.
The actual SEV-SNP initialization code was broken off into its own patch series . The patch series cover letter explains:
"These patches were originally included in v10 of the SNP KVM/hypervisor patches, but have been split off from the general KVM support for easier review and eventual merging into the x86 tree. They are based on linux-next to help stay in sync with both tip and kvm-next."
And then the v11 patches of the KVM hypervisor support include adapting to the split-off patch series, adjusting various ioctls, documentation improvements, code refactorings, and other improvements.
Hopefully it won't be too long into 2024 before all of the AMD SEV-SNP code is finally upstreamed for mainline Linux kernel builds.