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In the original Arm v8 two-stage translation, both stage 1 and stage 2 specify memory attributes (memory type, cacheability, shareability); these are then combined to produce the overall memory attributes for the whole stage 1+2 access. In QEMU we implement this by having get_phys_addr() fill in an ARMCacheAttrs struct, and we convert both the stage 1 and stage 2 attribute bit formats to the same encoding (an 8-bit attribute value matching the MAIR_EL1 fields, plus a 2-bit shareability value). The new FEAT_S2FWB feature allows the guest to enable a different interpretation of the attribute bits in the stage 2 descriptors. These bits can now be used to control details of how the stage 1 and 2 attributes should be combined (for instance they can say "always use the stage 1 attributes" or "ignore the stage 1 attributes and always be Device memory"). This means we need to pass the raw bit information for stage 2 down to the function which combines the stage 1 and stage 2 information. Add a field to ARMCacheAttrs that indicates whether the attrs field should be interpreted as MAIR format, or as the raw stage 2 attribute bits from the descriptor, and store the appropriate values when filling in cacheattrs. We only need to interpret the attrs field in a few places: * in do_ats_write(), where we know to expect a MAIR value (there is no ATS instruction to do a stage-2-only walk) * in S1_ptw_translate(), where we want to know whether the combined S1 + S2 attributes indicate Device memory that should provoke a fault * in combine_cacheattrs(), which does the S1 + S2 combining Update those places accordingly. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20220505183950.2781801-2-peter.maydell@linaro.org |
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