Hyper-V supports the use of XMM registers to perform fast hypercalls.
This allows guests to take advantage of the improved performance of the
fast hypercall interface even though a hypercall may require more than
(the current maximum of) two input registers.

The XMM fast hypercall interface uses six additional XMM registers (XMM0
to XMM5) to allow the guest to pass an input parameter block of up to
112 bytes.

Add framework to read from XMM registers in kvm_hv_hypercall() and use
the additional hypercall inputs from XMM registers in kvm_hv_flush_tlb()
when possible.

Cc: Alexander Graf <graf@amazon.com>
Co-developed-by: Evgeny Iakovlev <eyakovl@amazon.de>
Signed-off-by: Evgeny Iakovlev <eyakovl@amazon.de>
Signed-off-by: Siddharth Chandrasekaran <sidcha@amazon.de>
Message-Id: <fc62edad33f1920fe5c74dde47d7d0b4275a9012.1622019134.git.sidcha@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>