According to the submission of KVM, Linux 5.14 will support a fast XMM hypercall of Hyper-V on KVM. The hypercall interface of Microsoft Hyper-V is a mechanism for calling guests and supports the concept of fast XMM hypercall. Each hypercall defines a set of input or output parameters. These parameters are specified according to the memory-based data structure. All elements of the input and output data structures are filled to a natural boundary of up to 8 bytes.
The fast XMM super call support allows certain calls to enjoy an optimized performance. And this fast super call interface uses six XMM registers, while a general super call can only use two general-purpose registers at most. Detailed information about fast XMM hypercall can be found in the Microsoft documentation.
At present, Amazon engineers have provided support for the fast XMM super call of Hyper-V in KVM and have entered the “-next” branch of kvm.git. If there is no accident, it will be merged in the cycle of Linux 5.14. At the same time, Amazon is planning to contribute more Linux kernel patches to other super call interfaces that utilize this feature.