Comment 2 for bug 1756866

Skipping the following patches:
   * x86/kvm: Update spectre-v1 mitigation
   * x86/spectre: Report get_user mitigation for spectre_v1
   * nl80211: Sanitize array index in parse_txq_params
   * vfs, fdtable: Prevent bounds-check bypass via speculative execution
   * x86/syscall: Sanitize syscall table de-references under speculation
   * x86/get_user: Use pointer masking to limit speculation
   * x86: Introduce barrier_nospec
   * x86: Implement array_index_mask_nospec
   * array_index_nospec: Sanitize speculative array de-references
   * Documentation: Document array_index_nospec

This is upstream's implementation of Spectre v1 for Intel which is different than what we currently have in Xenial. We need to review it first to make sure we're not regressing, before we pull it in.