Add basic support for loongarch64 architecture

[heiher]

Summary of the PR

Add basic support for loongarch64 architecture.

Requirements

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[roypat]

Hi!
Before merging support for any new architecture, we'll definitely need some testing setup, similar to what we did with riscv recently (cc @TimePrinciple). But before any of that even I'd be interesting in learning more about the usecase for this. Are there any downstream projects based on rust-vmm that would like to support this architecture? E.g. riscv support was driving by CloudHypervisor wanting to support it. I don't think we should take on the maintenance burden of new architectures without any users :/

[Dandan336]

Hi maintainers,

Compiling the rust-kvm-ioctls failed for loong64 in the Debian Package Auto-Building environment.
Some of the error logs is as follows,

error[E0432]: unresolved import `kvm_bindings::kvm_device_attr`
  --> src/ioctls/device.rs:11:5
   |
11 | use kvm_bindings::kvm_device_attr;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `kvm_device_attr` in the root

warning: `vmm-sys-util` (lib) generated 3 warnings
error[E0425]: cannot find value `KVMIO` in this scope
  --> src/kvm_ioctls.rs:14:35
   |
14 | ioctl_io_nr!(KVM_GET_API_VERSION, KVMIO, 0x00);
   |                                   ^^^^^ not found in this scope

The full build log can be found at https://buildd.debian.org/status/logs.php?pkg=rust-kvm-ioctls&arch=loong64.
We need to add LoongArch64 support to upstream first.
The Homepage of Debian rust-kvm-ioctls source package is https://github.com/rust-vmm/kvm-ioctls.
Your opinions are welcome.

[TimePrinciple]

Hi @heiher @Dandan336, thanks for reaching out and sorry for my late reply.

As @roypat said earlier, we introduced support for RISC-V because our downstream projects like Cloud-Hypervisor and etc. are demanding it. I'm afraid package like rust-kvm-ioctls could not be built is not a very good reason for us to take additional architecture forward.

If you want rust-kvm-ioctls to build you can put your work in a patch and apply it while building, and if you have better reason other than this please share with us 🙂