Some processors may incur a machine check error possibly
resulting in an unrecoverable cpu hang when an instruction fetch
encounters a TLB multi-hit in the instruction TLB. This can occur
when the page size is changed along with either the physical
address or cache type [1].

This issue affects both bare-metal x86 page tables and EPT.

This can be mitigated by either eliminating the use of large
pages or by using careful TLB invalidations when changing the
page size in the page tables.

Just like Spectre, Meltdown, L1TF and MDS, a new bit has been
allocated in MSR_IA32_ARCH_CAPABILITIES (PSCHANGE_MC_NO) and will
be set on CPUs which are mitigated against this issue.

[1] For example please refer to erratum SKL002 in "6th Generation
Intel Processor Family Specification Update"
https://www.intel.com/content/www/us/en/products/docs/processors/core/desktop-6th-gen-core-family-spec-update.html
https://www.google.com/search?q=site:intel.com+SKL002

There are a lot of other affected processors outside of Skylake and
that the erratum(referred above) does not fully disclose the issue
and the impact, both on Skylake and across all the affected CPUs.
Signed-off-by: Vineela Tummalapalli <vineela.tummalapalli@intel.com>
Co-developed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

CVE-2018-12207

[tyhicks: Backport to 4.15
 - ATOM_SILVERMONT_D is ATOM_SILVERMONT_X
 - ATOM_AIRMONT_NP does not yet exist
 - ATOM_GOLDMONT_D is ATOM_GOLDMONT_X
 - Hygon isn't supported to VULNWL_HYGON() does not exist]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>