Merge branch kvm-arm64/configurable-id-regs into kvmarm/next

Merge branch kvm-arm64/configurable-id-regs into kvmarm/next

* kvm-arm64/configurable-id-regs:
  : Configurable ID register infrastructure, courtesy of Jing Zhang
  :
  : Create generalized infrastructure for allowing userspace to select the
  : supported feature set for a VM, so long as the feature set is a subset
  : of what hardware + KVM allows. This does not add any new features that
  : are user-configurable, and instead focuses on the necessary refactoring
  : to enable future work.
  :
  : As a consequence of the series, feature asymmetry is now deliberately
  : disallowed for KVM. It is unlikely that VMMs ever configured VMs with
  : asymmetry, nor does it align with the kernel's overall stance that
  : features must be uniform across all cores in the system.
  :
  : Furthermore, KVM incorrectly advertised an IMP_DEF PMU to guests for
  : some time. Migrations from affected kernels was supported by explicitly
  : allowing such an ID register value from userspace, and forwarding that
  : along to the guest. KVM now allows an IMP_DEF PMU version to be restored
  : through the ID register interface, but reinterprets the user value as
  : not implemented (0).
  KVM: arm64: Rip out the vestiges of the 'old' ID register scheme
  KVM: arm64: Handle ID register reads using the VM-wide values
  KVM: arm64: Use generic sanitisation for ID_AA64PFR0_EL1
  KVM: arm64: Use generic sanitisation for ID_(AA64)DFR0_EL1
  KVM: arm64: Use arm64_ftr_bits to sanitise ID register writes
  KVM: arm64: Save ID registers' sanitized value per guest
  KVM: arm64: Reuse fields of sys_reg_desc for idreg
  KVM: arm64: Rewrite IMPDEF PMU version as NI
  KVM: arm64: Make vCPU feature flags consistent VM-wide
  KVM: arm64: Relax invariance of KVM_ARM_VCPU_POWER_OFF
  KVM: arm64: Separate out feature sanitisation and initialisation

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>