CVE-2018-15468

An issue was discovered in Xen through 4.11.x. The DEBUGCTL MSR contains
several debugging features, some of which virtualise cleanly, but some do
not. In particular, Branch Trace Store is not virtualised by the processor,
and software has to be careful to configure it suitably not to lock up the
core. As a result, it must only be available to fully trusted guests.
Unfortunately, in the case that vPMU is disabled, all value checking was
skipped, allowing the guest to choose any MSR_DEBUGCTL setting it likes. A
malicious or buggy guest administrator (on Intel x86 HVM or PVH) can lock
up the entire host, causing a Denial of Service.

Notes