kvm_rs/kvm.rs
1// SPDX-License-Identifier: MIT
2//
3// Copyright (c) 2021, Johannes Stoelp <dev@memzero.de>
4
5//! KVM system ioctls.
6
7use std::fs;
8use std::io;
9use std::os::unix::io::FromRawFd;
10
11use crate::cap::{CapBool, CapInt};
12use crate::vm::Vm;
13use crate::{ioctl, kvm_sys, libcret};
14
15/// Wrapper for `/dev/kvm` ioctls.
16///
17/// Representation of the file descriptor obtained by opening `/dev/kvm`.
18/// This wrapper provides access to the `system ioctls` as described in [KVM API][kvm].
19///
20/// [kvm]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#general-description
21pub struct Kvm {
22 kvm: fs::File,
23}
24
25impl Kvm {
26 /// Open the `/dev/kvm` device.
27 pub fn new() -> io::Result<Kvm> {
28 let kvm = libcret(unsafe {
29 libc::open("/dev/kvm\0".as_ptr().cast(), libc::O_RDWR | libc::O_CLOEXEC)
30 })
31 .map(|fd| unsafe { fs::File::from_raw_fd(fd) })?;
32
33 assert_eq!(
34 kvm_sys::KVM_API_VERSION,
35 ioctl(&kvm, kvm_sys::KVM_GET_API_VERSION, 0)?
36 );
37
38 Ok(Kvm { kvm })
39 }
40
41 fn get_vpcu_mmap_size(&self) -> io::Result<usize> {
42 ioctl(&self.kvm, kvm_sys::KVM_GET_VCPU_MMAP_SIZE, 0).map(|size| size as usize)
43 }
44
45 /// Create a new virtual machine with the [`KVM_CREATE_VM`][kvm-create-vm] ioctl.
46 /// Returns a wrapper [`vm::Vm`][crate::vm::Vm] representing the VM.
47 ///
48 /// [kvm-create-vm]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#kvm-create-vm
49 pub fn create_vm(&self) -> io::Result<Vm> {
50 let vm = ioctl(&self.kvm, kvm_sys::KVM_CREATE_VM, 0 /* machine id */)
51 .map(|fd| unsafe { fs::File::from_raw_fd(fd) })?;
52
53 let vcpu_mmap_size = self.get_vpcu_mmap_size()?;
54
55 Ok(Vm::new(vm, vcpu_mmap_size))
56 }
57
58 /// Check availability of an extension with the [`KVM_CHECK_EXTENSION`][kvm-check-extension]
59 /// ioctl.
60 ///
61 /// [kvm-check-extension]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#kvm-check-extension
62 pub fn check_extenstion(&self, cap: CapBool) -> bool {
63 let ret = ioctl(&self.kvm, kvm_sys::KVM_CHECK_EXTENSION, cap.into());
64
65 matches!(ret, Ok(ret) if ret > 0)
66 }
67
68 /// Check availability of an extension with the [`KVM_CHECK_EXTENSION`][kvm-check-extension]
69 /// ioctl.
70 ///
71 /// [kvm-check-extension]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#kvm-check-extension
72 pub fn check_extenstion_int(&self, cap: CapInt) -> i32 {
73 let ret = ioctl(&self.kvm, kvm_sys::KVM_CHECK_EXTENSION, cap.into());
74
75 ret.unwrap_or(0)
76 }
77}