Let's assume there is significant value in backing non-CoCo VMs with 1GiB pages, unless you want to re-litigate the existence of 1GiB support in HugeTLBFS. If we assume 1GiB support is mandatory for non-CoCo VMs, then it becomes mandatory for CoCo VMs as well, because it's the only realistic way to run CoCo VMs and non-CoCo VMs on a single host. Mixing 1GiB HugeTLBFS with any other backing store for VMs simply isn't tenable due to the nature of 1GiB allocations. E.g. grabbing sub-1GiB chunks of memory for CoCo VMs quickly fragments memory to the point where HugeTLBFS can't allocate memory for non-CoCo VMs. Teaching HugeTLBFS to play nice with TDX and SNP isn't happening, which leaves adding 1GiB support to guest_memfd as the only way forward. Any boost to TDX (or SNP) performance is purely a bonus.
