14.3.4. Domains

In the ARMv8-A Architecture, the term domain is used to refer to a set of primary bus masters. Domains determine which of the masters are snooped, for coherent transactions. Snooping is the checking of the master’s cache to see whether the requested location is stored there. There are four defined domain types:

Typical system use is that masters running under the same operating system are in the same Inner Shareable domain. Masters that are sharing cacheable data, but that are not so closely coupled, are in the same Outer Shareable domain. Masters in the same inner domain must also be in the same outer domain. Domain selection for memory accesses is controlled through entries in the page tables.

Figure 14.5. Bus master coherency domains

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