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.
 mdeslaur> hypervisor packages are in universe. For
 mdeslaur> issues in the hypervisor, add appropriate
 mdeslaur> tags to each section, ex:
 mdeslaur> Tags_xen: universe-binary
Source: xen (LP Ubuntu Debian)
Upstream:released (4.11.1~pre.20180911.5acdd26fdc+dfsg-2)
Ubuntu 12.04 ESM (Precise Pangolin):DNE
Ubuntu 14.04 ESM (Trusty Tahr):DNE (trusty was needs-triage)
Ubuntu 16.04 LTS (Xenial Xerus):needed
Ubuntu 18.04 LTS (Bionic Beaver):needed
Ubuntu 19.04 (Disco Dingo):needed
Ubuntu 19.10 (Eoan):needed
Binaries built from this source package are in universe and so are supported by the community. For more details see
More Information

Updated: 2019-09-19 14:44:56 UTC (commit d32ebc32606b9517c6fa7d65a15441e2a57a6de5)