On Mon, Feb 05, 2018 at 09:19:46AM +1300, Michael Clark wrote: > BTW I've created branches in my own personal trees for Privileged ISA > v1.9.1. These trees are what I use for v1.9.1 backward compatibility > testing in QEMU: > > - https://github.com/michaeljclark/riscv-linux/tree/riscv-linux-4.6.2 > - https://github.com/michaeljclark/riscv-pk/tree/bbl-1.9.1
What MMU-enabled chips that implement 1.9.1 are out there? If there is enough we should support this with a compile time option in the Linux kernel as well. > We need to be a little more disciplined with software releases, especially > when there are backward incompatible changes in the specification. The > repos need to be branched and tagged. It should be possible to somehow > derive the conformance level. Perhaps the SBI should have an API for this. > This is one of the driving reasons behind adding version conformance levels > to QEMU. Previously we had repos in a state of flux and if you didn't have > the magic commit ids you were out of luck. For example, when we have > priv isa v1.11 released, we will still need a priv isa v1.10 mode which > masks out all of the new features. Given there are no "feature bits" > besides the extensions "IMAFDSU", all we have to go on presently is the > privileged ISA spec version number. As far as I can tell privileged ISA changes post 1.10 should be backwards compatible and only implemement detectable optional CSRs and instructions. That being said I started a thread on that on the privileged spec list where I need to follow up on Andrews mail once I get back to my work mail after a little vacation.
