Merge remote-tracking branch 'remotes/ehabkost/tags/x86-next-pull-request' into staging

Merge remote-tracking branch 'remotes/ehabkost/tags/x86-next-pull-request' into staging

x86 fixes for -rc1

Fixes for x86 that missed hard freeze:
* Don't trigger warnings for features set by
  CPU model versions (Xiaoyao Li)
* Missing features in Icelake-Server, Skylake-Server,
  Cascadelake-Server CPU models (Chenyi Qiang)
* Fix hvf x86_64 guest boot crash (Roman Bolshakov)

# gpg: Signature made Thu 16 Jul 2020 19:17:18 BST
# gpg:                using RSA key 5A322FD5ABC4D3DBACCFD1AA2807936F984DC5A6
# gpg:                issuer "[email protected]"
# gpg: Good signature from "Eduardo Habkost <[email protected]>" [full]
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/x86-next-pull-request:
  i386: hvf: Explicitly set CR4 guest/host mask
  target/i386: add the missing vmx features for Skylake-Server and Cascadelake-Server CPU models
  target/i386: fix model number and add missing features for Icelake-Server CPU model
  target/i386: add fast short REP MOV support
  i386/cpu: Don't add unavailable_features to env->user_features
  i368/cpu: Clear env->user_features after loading versioned CPU model

Signed-off-by: Peter Maydell <[email protected]>