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XUANTIE-RV / thead-extension-spec

XuanTie vendor extension Instruction Set spec
Apache License 2.0
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Introduce th.mxstatus CSR #45

Closed cmuellner closed 5 months ago

cmuellner commented 5 months ago

To implement proper extension discovery, we need to specify a mechanism to identify the availability of XThead* extension in a system. This mechanism already exists with the th.mxstatus register's THEADISAEE bit. Let's document this CSR.

Other bits than THEADISAEE are either 0 or defined as WPRI. This allows to define them in other extensions (e.g. UCME is defined as part of XTheadCmo and MAEE is defined as part of XTheadMaee).

The th.mxstatus CSR is defined to be available on all system's with a mvendorid or 0x5B7.

cmuellner commented 5 months ago

Ping @romanheros @Cooper-Qu

cmuellner commented 5 months ago

There was some good feedback in reponse to the SW enablement patches. This has led to dropping this PR in favor of #46 (i.e., documenting th.sxstatus instead of th.mxstatus).