This seems like it would work for a lot of use cases. The main one where it would fall down is if there's no page table entry for a given virtual address. Fixing that gets really hairy though, so it makes sense to have something like this for now.

I have a few comments so far:

1. Please fix the style issues that caused the build to fail. OpenOCD has a strict style guide, and I'm trying to keep our fork of it clean to facilitate upstreaming.
2. You're adding an extra command to the read/write program buffer programs. At least SiFive cores keep progbuf size to a minimum (2 instructions) so this will cause all memory access to fail. Can you add logic to only add these crc*i instructions when they'll actually be doing something?
3. Reading/writing memory (especially a few words) already has a lot of overhead, and this adds to it. It's worth thinking about only changing mstatus when halting/just before resuming.

Thanks for the feedback!

1. I've fixed the style issues
2. The csr-instructions to set and clear mprven are now only added to the program buffer if
   • progbufsize is at least 4
   • and mprv is set
3. I've reduced the average number of reads/writes. If progbufsize >= 4, the change now adds 2 register reads per memory access. If we furthermore do not come from m-mode, it adds another 2 register writes per access. Reading/writing when halting/resuming definitely sounds reasonable. However I couldn't find a short solution to prevent interferences with accesses to mstatus from other places during debug mode

Is there anything to add? And is it okay to leave out targets with a smaller program buffer for now or how would you suggest to proceed?

I've included your suggestions, in particular a configuration option to enable this feature. By default it is disabled now to prevent any confusion, but to me enabling it looks generally more intuitive. Perhaps changing the default behavior would be something for a release where people expect changes in the ui?

Do you have further comments or suggestions?

Done. Anything else?

Thanks for making this all nice and clean.