Wei Liu 85c0725f5c virtio-devices: signal queue eventfd for PCI_CFG doorbells ...

A virtqueue notification (doorbell) is normally delivered to the device
through an ioeventfd registered on the notify address, so a plain MMIO
write to the notify register is consumed by the hypervisor and never
reaches write_bar().

It does reach write_bar() when the driver rings the doorbell through the
VIRTIO_PCI_CAP_PCI_CFG window (write_cap_pci_cfg -> write_bar) instead
of a mapped BAR, or on backends that deliver the write to the VMM such
as SEV-SNP.

The notification arm of write_bar() only re-signalled the matching
queue eventfd under the sev_snp feature and logged an error
otherwise, so a doorbell delivered through the PCI_CFG window was
silently dropped on standard builds and the queue was never
processed.

The virtio spec allows driving the device purely through the PCI_CFG
window, so signal the matching queue eventfd for any doorbell that
reaches write_bar() on every build.

Add unit tests that ring a queue's doorbell via write_bar() and
assert only the addressed queue's eventfd is signalled.

Signed-off-by: Wei Liu <liuwe@microsoft.com>
Assisted-by: Copilot:Opus-4.8

2026-07-09 21:06:20 +00:00

..

src

virtio-devices: signal queue eventfd for PCI_CFG doorbells

2026-07-09 21:06:20 +00:00

build.rs

build: Add "fuzzing" as a valid cfg(..) attribute

2024-05-08 08:10:28 +00:00

Cargo.toml

virtio-devices: Use SmallVec for descriptor chains

2026-07-08 02:15:19 +00:00