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vmm: memory_manager: Make backing file from snapshot optional

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Let's not assume that a backing file is going to be the result from
a snapshot for each memory region. These regions might be backed by
a file on the host filesystem (not a temporary file in host RAM), which
means they don't need to be copied and stored into dedicated files.

That's why this commit prepares for further changes by introducing an
optional PathBuf associated with the snapshot of each memory region.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is contained in:
Sebastien Boeuf 2020-08-21 13:13:24 +02:00 committed by Samuel Ortiz
parent 871138d5cc
commit d1ce52f3a8
1 changed files with 25 additions and 19 deletions
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44
vmm/src/memory_manager.rs
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@ -380,7 +380,7 @@ impl MemoryManager {
for region in ext_regions.iter() {
mem_regions.push(MemoryManager::create_ram_region(
&Some(region.backing_file.clone()),
&region.backing_file,
0,
region.start_addr,
region.size as usize,
@ -600,9 +600,11 @@ impl MemoryManager {
let mut ext_regions = mem_snapshot.memory_regions;
for region in ext_regions.iter_mut() {
let mut memory_region_path = vm_snapshot_path.clone();
memory_region_path.push(region.backing_file.clone());
region.backing_file = memory_region_path;
if let Some(backing_file) = &mut region.backing_file {
let mut memory_region_path = vm_snapshot_path.clone();
memory_region_path.push(backing_file.clone());
*backing_file = memory_region_path;
}
}
// In case there was no backing file, we can safely use CoW by
@ -621,20 +623,24 @@ impl MemoryManager {
// new regions so that we can still use MAP_SHARED when restoring
// the VM.
guest_memory.memory().with_regions(|index, region| {
// Open (read only) the snapshot file for the given region.
let mut memory_region_file = OpenOptions::new()
.read(true)
.open(&ext_regions[index].backing_file)
.map_err(|e| Error::Restore(MigratableError::MigrateReceive(e.into())))?;
if let Some(backing_file) = &ext_regions[index].backing_file {
// Open (read only) the snapshot file for the given region.
let mut memory_region_file = OpenOptions::new()
.read(true)
.open(backing_file)
.map_err(|e| {
Error::Restore(MigratableError::MigrateReceive(e.into()))
})?;
// Fill the region with the file content.
region
.read_from(
MemoryRegionAddress(0),
&mut memory_region_file,
region.len().try_into().unwrap(),
)
.map_err(|e| Error::Restore(MigratableError::MigrateReceive(e.into())))?;
// Fill the region with the file content.
region
.read_from(
MemoryRegionAddress(0),
&mut memory_region_file,
region.len().try_into().unwrap(),
)
.map_err(|e| Error::Restore(MigratableError::MigrateReceive(e.into())))?;
}
Ok(())
})?;
@ -1510,7 +1516,7 @@ pub struct GuestAddressDef(pub u64);
#[derive(Serialize, Deserialize)]
pub struct MemoryRegion {
backing_file: PathBuf,
backing_file: Option<PathBuf>,
#[serde(with = "GuestAddressDef")]
start_addr: GuestAddress,
size: GuestUsize,
@ -1545,7 +1551,7 @@ impl Snapshottable for MemoryManager {
}
memory_regions.push(MemoryRegion {
backing_file: PathBuf::from(format!("memory-region-{}", index)),
backing_file: Some(PathBuf::from(format!("memory-region-{}", index))),
start_addr: region.start_addr(),
size: region.len(),
});