Merge "docs(spm): document s-el0 partition support" into integration
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@ -1063,6 +1063,36 @@ streams.
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Fault handling, Performance Monitor Extensions, Event Handling, MPAM.
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- No support for independent peripheral devices.
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S-EL0 Partition support
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=========================
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The SPMC (Hafnium) has limited capability to run S-EL0 FF-A partitions using
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FEAT_VHE (mandatory with ARMv8.1 in non-secure state, and in secure world
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with ARMv8.4 and FEAT_SEL2).
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S-EL0 partitions are useful for simple partitions that don't require full
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Trusted OS functionality. It is also useful to reduce jitter and cycle
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stealing from normal world since they are more lightweight than VMs.
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S-EL0 partitions are presented, loaded and initialized the same as S-EL1 VMs by
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the SPMC. They are differentiated primarily by the 'exception-level' property
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and the 'execution-ctx-count' property in the SP manifest. They are host apps
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under the single EL2&0 Stage-1 translation regime controlled by the SPMC and
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call into the SPMC through SVCs as opposed to HVCs and SMCs. These partitions
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can use FF-A defined services (FFA_MEM_PERM_*) to update or change permissions
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for memory regions.
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S-EL0 partitions are required by the FF-A specification to be UP endpoints,
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capable of migrating, and the SPMC enforces this requirement. The SPMC allows
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a S-EL0 partition to accept a direct message from secure world and normal world,
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and generate direct responses to them.
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Memory sharing between and with S-EL0 partitions is supported.
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Indirect messaging, Interrupt handling and Notifications are not supported with
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S-EL0 partitions and is work in progress, planned for future releases.
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All S-EL0 partitions must use AArch64. AArch32 S-EL0 partitions are not
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supported.
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References
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==========
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