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vmm: Refactor locking in AddressManager::move_bar

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The current implementation performs multiple operations on allocators in
a row, with the single goal of updating the allocator. For each of these
operations, the `Mutex` guarding the respective allocator is locked anew
which introduces room for race conditions.

Instead of locking the mutex multiple times, we should lock it once to
perform the whole move.

Signed-off-by: Pascal Scholz <pascal.scholz@cyberus-technology.de>
On-behalf-of: SAP pascal.scholz@sap.com
This commit is contained in:
Pascal Scholz
2026-02-24 14:39:45 +01:00
committed by Rob Bradford
parent c9cf3294ea
commit 15d1f1d7fd
1 changed files with 12 additions and 21 deletions
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33
vmm/src/device_manager.rs
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@@ -743,15 +743,10 @@ impl DeviceRelocation for AddressManager {
) -> std::result::Result<(), std::io::Error> {
match region_type {
PciBarRegionType::IoRegion => {
let mut sys_allocator = self.allocator.lock().unwrap();
// Update system allocator
self.allocator
.lock()
.unwrap()
.free_io_addresses(GuestAddress(old_base), len as GuestUsize);
self.allocator
.lock()
.unwrap()
sys_allocator.free_io_addresses(GuestAddress(old_base), len as GuestUsize);
sys_allocator
.allocate_io_addresses(Some(GuestAddress(new_base)), len as GuestUsize, None)
.ok_or_else(|| io::Error::other("failed allocating new IO range"))?;
@@ -761,26 +756,22 @@ impl DeviceRelocation for AddressManager {
.map_err(io::Error::other)?;
}
PciBarRegionType::Memory32BitRegion | PciBarRegionType::Memory64BitRegion => {
let allocators = if region_type == PciBarRegionType::Memory32BitRegion {
let pci_mmio_allocators = if region_type == PciBarRegionType::Memory32BitRegion {
&self.pci_mmio32_allocators
} else {
&self.pci_mmio64_allocators
};
// Find the specific allocator that this BAR was allocated from and use it for new one
for allocator in allocators {
let allocator_base = allocator.lock().unwrap().base();
let allocator_end = allocator.lock().unwrap().end();
// Find the specific allocator that this BAR was allocated from and use it for a new one
for pci_mmio_allocator_mutex in pci_mmio_allocators {
let mut pci_mmio_allocator = pci_mmio_allocator_mutex.lock().unwrap();
if old_base >= allocator_base.0 && old_base <= allocator_end.0 {
allocator
.lock()
.unwrap()
.free(GuestAddress(old_base), len as GuestUsize);
if old_base >= pci_mmio_allocator.base().0
&& old_base <= pci_mmio_allocator.end().0
{
pci_mmio_allocator.free(GuestAddress(old_base), len as GuestUsize);
allocator
.lock()
.unwrap()
pci_mmio_allocator
.allocate(Some(GuestAddress(new_base)), len as GuestUsize, Some(len))
.ok_or_else(|| io::Error::other("failed allocating new MMIO range"))?;