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hypervisor: refactor vec_with_array_field function

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refactor vec_with_array_field to common hypervisor code
so that mshv can also make use of it.

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
This commit is contained in:
Vineeth Pillai 2021-03-10 16:26:30 -05:00 committed by Samuel Ortiz
parent b8c0cd5cd4
commit 7fad74cb04
2 changed files with 31 additions and 30 deletions
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31
hypervisor/src/kvm/mod.rs
View File

@ -16,6 +16,7 @@ pub use crate::aarch64::{
use crate::cpu;
use crate::device;
use crate::hypervisor;
use crate::vec_with_array_field;
use crate::vm::{self, VmmOps};
#[cfg(target_arch = "aarch64")]
use crate::{arm64_core_reg_id, offset__of};
@ -110,36 +111,6 @@ pub struct KvmVm {
state: KvmVmState,
}
// 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);
v.resize_with(rounded_size, 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.
use std::mem::size_of;
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)
}
///
/// Implementation of Vm trait for KVM
/// Example:

30
hypervisor/src/lib.rs
View File

@ -72,3 +72,33 @@ pub fn new() -> std::result::Result<Arc<dyn Hypervisor>, HypervisorError> {
Ok(Arc::new(hv))
}
// 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);
v.resize_with(rounded_size, 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.
use std::mem::size_of;
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)
}