Eliminating fine grained timers in Xen
Bhanu C. Vattikonda, Sambit Kumar Das, Hovav Shacham · 2011
The move to "infrastructure-as-a-service" cloud computing brings with it a new risk: cross-virtual machine side channels through shared physical resources such as the L2 cache. One approach to this risk is to rewrite sensitive code to eliminate the signal. In this paper we consider another approach: weakening malicious virtual machines' ability to receive the signal by eliminating fine-grained timers. Such "fuzzy time" was implemented in 1991 in the VAX security kernel, but it was not clearly applicabile to modern virtual machine managers such as Xen on platforms such as the x86, which exports a cycle counter through the RDTSC instruction.