Within KVM for the x86 space is improved hashing in the MMU, faster PageLRU tracking, prep work for live migration support of nested hypervisors, host-to-guest PTP support, and various other optimizations. Great to see all the performance tuning going on for KVM x86 and can't wait to get to a fresh round of Linux virtualization benchmarking.
In the ARM space there is GIVv3 save/restore support, physical timer emulation, and various fixes. The KVM MIPS code also saw various low-level improvements as well as support for SMP guests and a large rewrite of its MMU emulation code.
KVM on PowerPC meanwhile received support for POWER9 using the radix-tree MMU, a resizable hashed page table, and other bug fixes. Likewise, the s390 architecture code also received more fixes and optimizations, support for more SIMD extensions, and other improvements.
More details on the KVM changes for Linux 4.11 via this pull request.