Can I utilize the RISC-V vector extension with QEMU?

[bithamr]

Hello!

For the last few days I've been trying to see if it's possible to run a RISC-V 
QEMU instance that has v1.0 vector extension enabled:

https://github.com/riscv/riscv-v-spec/blob/master/v-spec.adoc

I found the following documentation:

https://wiki.qemu.org/Documentation/Platforms/RISCV
https://www.qemu.org/docs/master/system/target-riscv.html

In that documentation it references extensions, and how some of them might be 
enabled with "-x", so it seems like it might be possible? But overall between 
both the wiki and the documentation is was unclear if any of the virtual CPUs 
present in qemu today actually support the vector extensions (and if so how to 
enable that).

What I have so far is a copy of Fedora running in a RISC-V virtual machine for 
testing. I found the following virtual CPUs come packaged in with 
qemu-riscv64-static:

```
rv64
shakti-c
sifive-e51
sifive-u54
thead-c906
veyron-v1
x-rv128
```

However I have started the virtual machine up with each of these CPUs and 
tested them using the following program:

```
.section .text
.global _start

_start:
    vsetvli x0, x0, e8, m1
    li a7, 93
    li a0, 0
    ecall
```

Each of them returns the following:

```
$ as -o check.o check.s
check.s:5: Error: unrecognized opcode `vsetvli x0,x0,e8,m1', extension `v' or 
`zve64x' or `zve32x' required
```

I'm kinda getting stuck so I thought maybe it was time to reach out for some 
help, I really appreciate any you can provide: can I, and then HOW can I run a 
RISC-V qemu instance that has the vector extension present?

Thank you!

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