The HSA Foundation has produced the HSA Platform System Architecture
Specification that goes a long way towards addressing the need for a clear and
consistent method for specifying weakly consistent memory. HSA is specified in
a natural language which makes it open to multiple ambiguous interpretations
and could render bugs in implementations of it in hardware and software. In
this paper we present a formal model of HSA which can be used in the
development and verification of both concurrent software applications as well
as in the development and verification of the HSA-compliant platform itself. We
use the Event-B language to build a provably correct hierarchy of models from
the most abstract to a detailed refinement of HSA close to implementation
level. Our memory models are general in that they represent an arbitrary number
of masters, programs and instruction interleavings. We reason about such
general models using refinements. Using Rodin tool we are able to model and
verify an entire hierarchy of models using proofs to establish that each
refinement is correct. We define an automated validation method that allows us
to test baseline compliance of the model against a suite of published HSA
litmus tests. Once we complete model validation we develop a coverage driven
method to extract a richer set of tests from the Event-B model and a user
specified coverage model. These tests are used for extensive regression testing
of hardware and software systems. Our method of refinement based formal
modelling, baseline compliance testing of the model and coverage driven test
extraction using the single language of Event-B is a new way to address a key
challenge facing the design and verification of multi-core systems.Comment: 9 pages, 10 figure