refactor(virtio-mem): define constants as MiB

Avoid multiple conversions back and forth from MiB to bytes by just
storing as MiB.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

src/firecracker/src/api_server/request/hotplug/memory.rs

@@ -25,8 +25,9 @@ pub(crate) fn parse_get_memory_hotplug() -> Result<ParsedRequest, RequestError>
 
 #[cfg(test)]
 mod tests {
-    use vmm::devices::virtio::mem::{VIRTIO_MEM_DEFAULT_BLOCK_SIZE, VIRTIO_MEM_DEFAULT_SLOT_SIZE};
-    use vmm::utils::bytes_to_mib;
+    use vmm::devices::virtio::mem::{
+        VIRTIO_MEM_DEFAULT_BLOCK_SIZE_MIB, VIRTIO_MEM_DEFAULT_SLOT_SIZE_MIB,
+    };
 
     use super::*;
     use crate::api_server::parsed_request::tests::vmm_action_from_request;
@@ -47,8 +48,8 @@ mod tests {
         }"#;
         let expected_config = MemoryHotplugConfig {
             total_size_mib: 2048,
-            block_size_mib: bytes_to_mib(VIRTIO_MEM_DEFAULT_BLOCK_SIZE),
-            slot_size_mib: bytes_to_mib(VIRTIO_MEM_DEFAULT_SLOT_SIZE),
+            block_size_mib: VIRTIO_MEM_DEFAULT_BLOCK_SIZE_MIB,
+            slot_size_mib: VIRTIO_MEM_DEFAULT_SLOT_SIZE_MIB,
         };
         assert_eq!(
             vmm_action_from_request(parse_put_memory_hotplug(&Body::new(body)).unwrap()),

src/vmm/src/devices/virtio/mem/mod.rs

@@ -13,8 +13,8 @@ pub(crate) const MEM_NUM_QUEUES: usize = 1;
 
 pub(crate) const MEM_QUEUE: usize = 0;
 
-pub const VIRTIO_MEM_DEFAULT_BLOCK_SIZE: usize = 2 << 20; // 2MiB
-pub const VIRTIO_MEM_DEFAULT_SLOT_SIZE: usize = 128 << 20; // 128 MiB
+pub const VIRTIO_MEM_DEFAULT_BLOCK_SIZE_MIB: usize = 2;
+pub const VIRTIO_MEM_DEFAULT_SLOT_SIZE_MIB: usize = 128;
 pub const VIRTIO_MEM_GUEST_ADDRESS: GuestAddress = GuestAddress(FIRST_ADDR_PAST_64BITS_MMIO); // 512GiB
 
 pub const VIRTIO_MEM_DEV_ID: &str = "mem";

src/vmm/src/vmm_config/memory_hotplug.rs

@@ -3,8 +3,9 @@
 
 use serde::{Deserialize, Serialize};
 
-use crate::devices::virtio::mem::{VIRTIO_MEM_DEFAULT_BLOCK_SIZE, VIRTIO_MEM_DEFAULT_SLOT_SIZE};
-use crate::utils::bytes_to_mib;
+use crate::devices::virtio::mem::{
+    VIRTIO_MEM_DEFAULT_BLOCK_SIZE_MIB, VIRTIO_MEM_DEFAULT_SLOT_SIZE_MIB,
+};
 
 /// Errors associated with memory hotplug configuration.
 #[derive(Debug, thiserror::Error, displaydoc::Display)]
@@ -24,11 +25,11 @@ pub enum MemoryHotplugConfigError {
 }
 
 fn default_block_size_mib() -> usize {
-    bytes_to_mib(VIRTIO_MEM_DEFAULT_BLOCK_SIZE)
+    VIRTIO_MEM_DEFAULT_BLOCK_SIZE_MIB
 }
 
 fn default_slot_size_mib() -> usize {
-    bytes_to_mib(VIRTIO_MEM_DEFAULT_SLOT_SIZE)
+    VIRTIO_MEM_DEFAULT_SLOT_SIZE_MIB
 }
 
 /// Configuration for memory hotplug device.
@@ -48,7 +49,7 @@ pub struct MemoryHotplugConfig {
 impl MemoryHotplugConfig {
     /// Validates the configuration.
     pub fn validate(&self) -> Result<(), MemoryHotplugConfigError> {
-        let min_block_size_mib = bytes_to_mib(VIRTIO_MEM_DEFAULT_BLOCK_SIZE);
+        let min_block_size_mib = VIRTIO_MEM_DEFAULT_BLOCK_SIZE_MIB;
         if self.block_size_mib < min_block_size_mib {
             return Err(MemoryHotplugConfigError::BlockSizeTooSmall(
                 min_block_size_mib,
@@ -58,7 +59,7 @@ impl MemoryHotplugConfig {
             return Err(MemoryHotplugConfigError::BlockSizeNotPowerOfTwo);
         }
 
-        let min_slot_size_mib = bytes_to_mib(VIRTIO_MEM_DEFAULT_SLOT_SIZE);
+        let min_slot_size_mib = VIRTIO_MEM_DEFAULT_SLOT_SIZE_MIB;
         if self.slot_size_mib < min_slot_size_mib {
             return Err(MemoryHotplugConfigError::SlotSizeTooSmall(
                 min_slot_size_mib,