Dennis HilkLinux diagnosticsDE

Virtual & unusual hardware

Virtio memory balloon over modern PCI

Ballooning is a guest-host memory-management function, not an ordinary RAM identification device.

Editorial source review: Share public profileOpen in the identification tool
On this page
  1. Overview & identity
  2. Driver & binding
  3. Firmware
  4. Read-only diagnostics
  5. Limitations & related issues
  6. References

Overview & identity

The checked modern PCI rule maps 1af4:1045 to virtio type 5 (balloon). This is a virtual function identity, not the host hardware model. Transitional PCI IDs use a different subsystem-ID rule and are deliberately not inferred here.

Curated identifiers
pci 1af4:1045

A numeric match establishes a candidate family within the reviewed evidence. Marketing names, board variants, subsystem conditions and successful operation remain separate questions.

Driver & binding

virtio_balloon handles type 5 and negotiates memory-management features with the host. A PCI match alone does not say whether the balloon is inflated, whether free-page reporting is active, or how much memory the host reclaimed. lspci can therefore correctly report virtio-pci while the child function is bound to virtio_balloon.

  • virtio_pci — kernel driver/module candidate
  • virtio_balloon — kernel driver/module candidate

Detected, bound, operational: learn the difference

Firmware

No host payload established here

No external firmware filename was established in the checked driver path. This does not describe firmware stored inside the device.

Inspect firmware packaging on your distribution

Read-only diagnostics

Run one displayed command at a time. Replace uppercase placeholders with the affected device, interface or module from your own output. Commands are never executed here. Read-only output can still contain private identifiers.

Inspect the PCI function and binding

lspci -nnk -s BDF

Replace BDF with the complete address, for example 0000:00:14.0. This read-only query needs pciutils and normally no sudo. “Kernel driver in use” is observed binding; “Kernel modules” lists candidates.

Inspect the virtio child function driver

ls -l /sys/bus/pci/devices/BDF/virtio*/driver

Replace BDF with the full observed PCI address. Read the child driver link without sudo; virtio_pci is the PCI transport, while this link belongs to the function driver. A missing child or link means that this layer was not observed.

Read guest memory accounting

cat /proc/meminfo

Read current guest counters without sudo. MemAvailable describes the guest’s estimate, not the amount assigned or reclaimed by a hypervisor; correlate it with workload and host observations.

Limitations & related issues

Guest memory pressure has many causes and must be correlated with host policy. Module presence and MemAvailable are useful context but cannot quantify host reclamation by themselves.

These guides are linked for relevant observations, not as known defects of every device in this family.

Choose a hardware diagnostic workflow · Inspect a log excerpt in Fix Lab

References

Source review records a checked implementation or document, not a reproduced hardware test. Version-specific tables do not establish a minimum kernel or guaranteed operation.