Add Zvma Extension

[unlsycn]

Related to the Zvma extension draft in SiFive proposal for RISC-V AME extension
Working in progress

[aswaterman]

I’d prefer for the AME TG to coalesce around a proposal before we merge any one of them into this repo. (Yes, that means I’m blocking a PR for an ISA extension I designed…)

[sequencer]

I’d prefer for the AME TG to coalesce around a proposal before we merge any one of them into this repo. (Yes, that means I’m blocking a PR for an ISA extension I designed…)

Sure, feel free to block it as you wish:) We just place it here, maintaining a patch for the RTL development.