cloud-hypervisor/vfio/src/lib.rs

// Copyright © 2019 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause
//

//#![deny(missing_docs)]
//! Virtual Function I/O (VFIO) API
extern crate byteorder;
extern crate devices;
extern crate kvm_bindings;
extern crate kvm_ioctls;
#[macro_use]
extern crate log;
extern crate pci;
extern crate vfio_bindings;
extern crate vm_allocator;
extern crate vm_memory;
#[macro_use]
extern crate vmm_sys_util;

mod vfio_device;
mod vfio_ioctls;
mod vfio_pci;

use std::mem::size_of;

pub use vfio_device::{VfioDevice, VfioError};
pub use vfio_pci::{VfioPciDevice, VfioPciError};

// Returns a `Vec<T>` with a size in bytes at least as large as `size_in_bytes`.
fn vec_with_size_in_bytes<T: Default>(size_in_bytes: usize) -> Vec<T> {
    let rounded_size = (size_in_bytes + size_of::<T>() - 1) / size_of::<T>();
    let mut v = Vec::with_capacity(rounded_size);
    for _ in 0..rounded_size {
        v.push(T::default())
    }
    v
}

// The kvm API has many structs that resemble the following `Foo` structure:
//
// ```
// #[repr(C)]
// struct Foo {
//    some_data: u32
//    entries: __IncompleteArrayField<__u32>,
// }
// ```
//
// In order to allocate such a structure, `size_of::<Foo>()` would be too small because it would not
// include any space for `entries`. To make the allocation large enough while still being aligned
// for `Foo`, a `Vec<Foo>` is created. Only the first element of `Vec<Foo>` would actually be used
// as a `Foo`. The remaining memory in the `Vec<Foo>` is for `entries`, which must be contiguous
// with `Foo`. This function is used to make the `Vec<Foo>` with enough space for `count` entries.
pub fn vec_with_array_field<T: Default, F>(count: usize) -> Vec<T> {
    let element_space = count * size_of::<F>();
    let vec_size_bytes = size_of::<T>() + element_space;
    vec_with_size_in_bytes(vec_size_bytes)
}