Linux 7.1 KVM Adds "Very Experimental" Support For pKVM Protected Guests

The Linux 7.1 merge window brings several KVM updates across architectures. On Arm, KVM gains highly experimental pKVM protected guest support, where pages are unmapped from the host as they fault into the guest and shared back via pKVM hypercalls — working toward full host isolation. This requires the CONFIG_ARM_PVKM_GUEST kernel option and the 'kvm-arm.mode=protected' boot parameter, and will taint the kernel. On s390, KVM adds ESA 31-bit guest support inside nested hypervisors. On x86, KVM now advertises AVX-512 BMM support for upcoming AMD Zen 6 processors. Minor AMD SEV-SNP changes and hardening improvements are also included.