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

x86 queue, 2018-01-17

Highlight: new CPU models that expose CPU features that guests
can use to mitigate CVE-2017-5715 (Spectre variant #2).

# gpg: Signature made Thu 18 Jan 2018 02:00:03 GMT
# gpg:                using RSA key 0x2807936F984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>"
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/x86-pull-request:
  i386: Add EPYC-IBPB CPU model
  i386: Add new -IBRS versions of Intel CPU models
  i386: Add FEAT_8000_0008_EBX CPUID feature word
  i386: Add spec-ctrl CPUID bit
  i386: Add support for SPEC_CTRL MSR
  i386: Change X86CPUDefinition::model_id to const char*
  target/i386: add clflushopt to "Skylake-Server" cpu model
  pc: add 2.12 machine types

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>