csrrs instruction illegal with proxy kernel? about rocket-rocc-examples

[hawkcl]

Very likely. Thanks a lot.

[seldridge]

Is it the csrrs instruction in the patch that is used to set the XS bits?

I have not run the proxy kernel using that patch in some time. However, there's circumstantial evidence that that approach, or something like it, should still work given that Gemmini is working with the proxy kernel.

[hawkcl]

It is the csrrs instruction in my testing code. I need to handle the RoCC interrupt in my testing code. I think Gemmini interrupt is used for address translation, and it is handled by the core.

[seldridge]

The user-level spec states:

Attempts to access a non-existent CSR raise an illegal instruction exception. Attempts to access a
CSR without appropriate privilege level or to write a read-only register also raise illegal instruction
exceptions.

I would interpret that as your csrrs instruction is running without sufficient privilege to do what you are trying to do. I think that if you run a test under the proxy kernel, that's user mode, while running bare metal is likely machine mode (this may be wrong).