A question of msdcfg.SDICN

[ZeyueShen]

When mmpt.Mode=Bare, according to smmtt spec, mmpt.sdid must be set to 0, which indicates that the current space is not in any supervisor domain. In this case, set msdcfg.SDICN to 0 or a valid number or an invalid number. Will it affect imsic and aplic (hart associated) address access? (Will an exception be reported when msdcfg.SDICN is set to invalid numbe or 0)?

[rsahita]

hi @ZeyueShen - these are orthogonal (not interdependent) aspects - MPT can be in bare mode, while the RDSM may specify the SDICN as required.

The rules based on how SDICN is programmed (0, !impl controller OR impl controller) are specified on page 39 of the spec. See text starting with "When SDICN is not the number of an implemented interrupt controller, or is zero then the following rules apply to all privilege modes:"

[ZeyueShen]

hi @rsahita - Thanks for your reply. According to your explanation, I understand that the choice of SDICN has nothing to do with whether mmpt.Mode is equal to 0.

But I have one more question: msdcfg is used to configure the current supervisor domain. When mmpt.Mode=Bare, mmpt.sdid=0, and supervisor domain in this case is meaningless (because mmpt.Mode=Bare). In this case, the configuration of SDICN is used to configure mmpt.sdid=0. Is this understanding correct? Or maybe my expression is not quite correct, I just want to know whether mmpt.sdid and SDICN are related?

[rock-ifly]

If Smsdia extension is implemented, then msdcfg.SDICN is non-zero at reset and holds the number of
an implemented supervisor domain interrupt controller.

P39 @ V0.2.0