Re: Smstateen for Zcmt


John Hauser
 

Tariq Kurd wrote:
Therefore, I'd like to allocate one Smstateen bit to JVT - the CSR only.
Can I allocate bit 2 as follows?
Yes, let's assume bit 2 is allocated for this purpose, in mstateen0,
hstateen0, and sstateen0.

*Bit 2 applies only for the case that Zcmt is implemented, which includes
the JVT CSR and the cm.jt, cm.jalt encodings.*
*For convenience if bit 2 of a controlling stateen0 CSR is zero, then all
cm.jt, cm.jalt instructions cause an illegal instruction trap *
*(or virtual instruction trap, if relevant). *

How does that sound?
We'll probably change the wording later, but for now, replace the
word _encodings_ by _instructions_, and drop "For convenience".
Instructions CM.JT and CM.JALT must trap because they implicitly depend
on the value of jvt.

..and I'm not proposing a stateen for Zcmb, Zcmp, Zcmpe.
Right. The intention is that stateen bits should be for controlling
access to new state. No state, no stateen bit.

- John Hauser

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