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 B.4.2. Mapping Fault

 A mapping fault occurs when the translation for the requested data is not in the hardware page table, but the data is resident in memory. The steps leading up to a mapping fault and how the fault is resolved follows. A mapping fault is in the data storage class of faults.

  1. The PSL successfully converts the effective address (EA) to a virtual address (VA).

  2. The PSL is unable to locate a hardware page table entry for converting the VA into a RA.

  3. The PSL sets the appropriate state in the PSL_DSISR_An Register (PSL_DSISR_An[DM,M]) and sends an interrupt to the associated operating system using LISN0.

  4. The operating system determines that the page is resident in memory, but a mapping is not in the hardware page table.

  5. The operating system updates the hardware page table with a mapping to the requested page and writes the PSL_TFC_An[R] bit to a '1' indicating that the PSL should restart the corresponding operation.

  6. The PSL restarts the operation and translates the EA to an RA. The PSL should find the mapping for the hardware page table.

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