The image needs to be available to the guest with a partition table and
a partition with a label named "nixos" so the stage1 can mount it. By
enabling the virtualisation.diskImage option we now have a persistent
root filesystem, including /home.

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/c3e128f3c0ecc1fb04aef9f72b3dcc2f6cecf370' (2024-01-15)
  → 'github:rodarima/nixpkgs/57e7c8fa4fdc414a936ce83afd0c70fb0a3a31d5' (2024-01-24)

There is a problem in the way pkgsStatic is constructed, causing our
-march argument to be missed, leading to binaries that fail to run. This
affects only security wrappers so far (mount, sudo, ...) but it will
likely affect any pkgsStatic binary.

The march and mtune flags are passed by the crossSystem gcc attributes,
which are placed *before* the flags to gcc. This may end up causing some
packages to break, but it is working fine so far.

It is currently causing a trap, but the reason is not clear:

nsncd[1179]: unhandled signal 7 code 0x1 at 0x00ffffff8184e920 in libc.so.6[ffffff81824000+1aa000]
CPU: 3 PID: 1179 Comm: nsncd Not tainted 6.1.72 #1-NixOS
Hardware name: riscv-virtio,qemu (DT)
epc : 00ffffff8184e920 ra : 00ffffff8184e868 sp : 00ffffffef6ab610
 gp : 00aaaaaac0f07db8 tp : 00ffffff81822780 t0 : 00ffffffef6ab1f0
 t1 : 00aaaaaac0e5283c t2 : 0000000000000b56 s0 : 00ffffffef6ab668
 s1 : 0000000000000001 a0 : 0000000000000001 a1 : 00ffffffef6ab668
 a2 : 00ffffffef6ab678 a3 : 00aaaaaac0f06e40 a4 : 0000000100000000
 a5 : 00aaaaaac0eac296 a6 : 00ffffff819d3048 a7 : 00ffffffef6ab8c0
 s2 : 0000000000000000 s3 : 00aaaaaac0efac40 s4 : 00aaaaaac0e6755a
 s5 : 00ffffffef6ab678 s6 : 00aaaaaac0efac48 s7 : 00ffffff81a2fd58
 s8 : 00ffffff81a30030 s9 : 00ffffffd7386ef0 s10: 0000000000000000
 s11: 0000000000000000 t3 : 00ffffff8184e818 t4 : 0000000000000028
 t5 : 00ffffff81a24380 t6 : 00ffffff81a074c8
status: 0000000200004020 badaddr: 00aaaaaac0eac296 cause: 0000000000000000

In order to build the kernel without compressed instructions we need to
disable EFI support. We also need to leave the kernel to figure the
proper -march and -mabi flags, as otherwise it fails to build. Using the
option "CONFIG_RISCV_ISA_C n" disables the use of compressed
instructions.

Prevents mass rebuilds in x86, where the envvar doesn't have any effect.

In QEMU the kernel is loaded at the ${kernel_addr_r} address and we need
to use booti instead of bootm.

Booting the kernel works, but by manually specifying the address.