Add extra extensions to RISC-V

[dramforever]

(Moved from: #199 (comment))

Can we get some extra extensions like vector, bit-manipulation and scalar crypto enabled? It seems that for user-mode emulation setting QEMU_CPU to rv64,v=on etc would do the trick, though it does require a sort of recent version of QEMU, and I'm not sure what's the minimum required and what's the version on the runner. I've tested on QEMU 7.1.0/7.0.0 and GCC 11.3.0.

I roughly checked https://gitlab.com/qemu-project/qemu/-/blob/master/target/riscv/cpu.c and it seems that passing argument -march=rv64gcv_zba_zbb_zbc_zbs_zbkx_zk_zks to GCC and environment QEMU_CPU=rv64,v=on,zbkx=on,zk=on,zks=on to QEMU should enable everything that QEMU supports.

Though it seems that the crypto ones (Zbk* and Zk*) are not supported on 7.0.0 yet though, so -march=rv64gcv_zba_zbb_zbc_zbs and QEMU_CPU=rv64,v=on would be a great start (Zb* are enabled on QEMU by default). In addition, on QEMU 7.1.0, it complains with a warning unless you add vext_spec=v1.0 like rv64,v=on,vext_spec=v1.0, so that's something to keep in mind.

I've written a kumite that should work (at least compile fine (at least should fail with a different message)) if the changes above are implemented: https://www.codewars.com/kumite/635ac4a48f20014af2cf522e

[dramforever]

What's the QEMU version on the runner host? The changelog says that QEMU supports the ratified vector extension starting from 7.0 only, so if we're going to go vectors we probably need to get at least 7.0 on the host: https://wiki.qemu.org/ChangeLog/7.0#RISC-V. 7.1 would be better because it will also add, as said, the crypto extensions: https://wiki.qemu.org/ChangeLog/7.1#RISC-V

[kazk]

The current version should be 6.x (6.23?). https://packages.ubuntu.com/focal/qemu-user-static
We should be able to upgrade to Ubuntu 22.04 and match GitHub's current ubuntu-latest to have 7.0.

[kazk]

Maybe we can use https://github.com/multiarch/qemu-user-static to get 7.1.

[kazk]

I'll install qemu-user-static 7.1 from .deb like codewars/riscv#9

[kazk]

Deployed

[dramforever]

Thanks! I've tried it on a few kata and it works great