This appears to avoid requiring KVM when it’s not available. This is
what I originally though -cpu host did. Unfortunately not much
documentation available from the QEMU side on this, but this appears
to square with help:
$ qemu-system-x86 -cpu help
...
x86 host KVM processor with all supported host features
x86 max Enables all features supported by the accelerator in the current host
...
Whether we actually want to support this not clear, since this only
happens when your CPU doesn’t have full KVM support. Some Nix builders
are lying about kvm support though. Things aren’t too slow without it
though.
Fixes https://github.com/NixOS/nixpkgs/issues/85394
Alternative to https://github.com/NixOS/nixpkgs/pull/83920
This modifies the `router` to not give out a range of IP addresses but
only give out a fixed address based on the MAC address using the
`services.dhcpd4.machines` option.
To get access to the MAC address the `qemuNicMac` function is defined
and exported from `qemu-flags.nix`.
Following legacy packing conventions, `isArm` was defined just for
32-bit ARM instruction set. This is confusing to non packagers though,
because Aarch64 is an ARM instruction set.
The official ARM overview for ARMv8[1] is surprisingly not confusing,
given the overall state of affairs for ARM naming conventions, and
offers us a solution. It divides the nomenclature into three levels:
```
ISA: ARMv8 {-A, -R, -M}
/ \
Mode: Aarch32 Aarch64
| / \
Encoding: A64 A32 T32
```
At the top is the overall v8 instruction set archicture. Second are the
two modes, defined by bitwidth but differing in other semantics too, and
buttom are the encodings, (hopefully?) isomorphic if they encode the
same mode.
The 32 bit encodings are mostly backwards compatible with previous
non-Thumb and Thumb encodings, and if so we can pun the mode names to
instead mean "sets of compatable or isomorphic encodings", and then
voilà we have nice names for 32-bit and 64-bit arm instruction sets
which do not use the word ARM so as to not confused either laymen or
experienced ARM packages.
[1]: https://developer.arm.com/products/architecture/a-profile
