socket: 0.956
virtual: 0.921
architecture: 0.888
performance: 0.877
device: 0.866
x86: 0.847
kernel: 0.843
network: 0.799
files: 0.781
VMM: 0.779
vnc: 0.779
graphic: 0.760
TCG: 0.759
hypervisor: 0.752
register: 0.711
ppc: 0.703
arm: 0.637
peripherals: 0.605
debug: 0.576
user-level: 0.575
PID: 0.573
risc-v: 0.570
semantic: 0.562
permissions: 0.562
mistranslation: 0.453
boot: 0.413
i386: 0.393
assembly: 0.351
KVM: 0.278

UNIX socket path is too long
Description of problem:
At [Unikraft](https://unikraft.org) we facilitate the construction and also runtime lifecycle management of ultra-lightweight virtual machine unikernels.  We have developed [`kraft`](https://github.com/unikraft/kraftkit), an open-source tool which facilitates this across a number of different virtual machine monitors, [including QEMU](https://github.com/unikraft/kraftkit/tree/staging/machine/qemu).

We are receiving increased reports of the following error from our users:

```
could not start and wait for QEMU process: qemu-system-x86_64: -qmp unix:/Users/__USERNAME__/.local/share/kraftkit/runtime/37a7691a-d402-4760-b493-692bb8d0460a/qemu_control.sock,server,nowait: UNIX socket path '/Users/__USERNAME__/.local/share/kraftkit/runtime/37a7691a-d402-4760-b493-692bb8d0460a/qemu_control.sock' is too long
```

We systematically build the relevant QEMU process command line and arguments with flags [via our Go SDK](https://github.com/unikraft/kraftkit/blob/staging/machine/qemu/v1alpha1.go#L180-L229) and include what has become an erroneously long UNIX path for the QAPI control socket which we use to manage instantiated VM instances.

This issue tracks the increasing of maximum path length for the `-qmp` (and maybe other) flags which accept paths.
Steps to reproduce:
1. Install [`kraft`](https://github.com/unikraft/kraftkit), [Unikraft](https://unikraft.org)'s companion command-line client;
2. Update KraftKit's config file to include an arbitrarily long path for `runtime_dir` by editing `~/.config/kraftkit/config.yaml`;
3. Start a QEMU unikernel instance with `kraft run --arch x86_64 --plat qemu unikraft.org/helloworld:latest`
Additional information: