From ecffd9494c1c907715dcaee7437db54878f81b1f Mon Sep 17 00:00:00 2001 From: Anatol Belski Date: Sun, 10 May 2026 00:55:53 +0200 Subject: [PATCH] virtio-devices: Test consume_config_change semantics Cover the three observable cases of consume_config_change. With the flag set the counter advances by one and the flag is cleared. With the flag clear the call is a no-op. A burst of flag sets between two reads results in only one bump, which is the wrap hazard mitigation the spec asks for. Signed-off-by: Anatol Belski --- .../src/transport/pci_common_config.rs | 44 +++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/virtio-devices/src/transport/pci_common_config.rs b/virtio-devices/src/transport/pci_common_config.rs index 7e9e5456e..eac14e5d2 100644 --- a/virtio-devices/src/transport/pci_common_config.rs +++ b/virtio-devices/src/transport/pci_common_config.rs @@ -588,4 +588,48 @@ mod unit_tests { .all(|v| *v == VIRTQ_MSI_NO_VECTOR) ); } + + fn make_regs(config_generation: u8) -> VirtioPciCommonConfig { + let dev: Arc> = Arc::new(Mutex::new(DummyDevice(0))); + VirtioPciCommonConfig { + device: dev, + driver_status: Arc::new(AtomicU8::new(0)), + config_generation: Arc::new(AtomicU8::new(config_generation)), + config_changed: Arc::new(AtomicBool::new(false)), + device_feature_select: 0, + driver_feature_select: 0, + queue_select: 0, + msix_config: Arc::new(AtomicU16::new(0)), + msix_queues: Arc::new(Mutex::new(vec![0; 1])), + } + } + + #[test] + fn consume_config_change_bumps_when_flag_set() { + let regs = make_regs(0x10); + regs.config_changed.store(true, Ordering::Release); + regs.consume_config_change(); + assert_eq!(regs.config_generation.load(Ordering::Acquire), 0x11); + assert!(!regs.config_changed.load(Ordering::Acquire)); + } + + #[test] + fn consume_config_change_is_noop_when_flag_clear() { + let regs = make_regs(0x10); + regs.consume_config_change(); + assert_eq!(regs.config_generation.load(Ordering::Acquire), 0x10); + assert!(!regs.config_changed.load(Ordering::Acquire)); + } + + #[test] + fn consume_config_change_coalesces_multiple_sets() { + let regs = make_regs(0x10); + regs.config_changed.store(true, Ordering::Release); + regs.config_changed.store(true, Ordering::Release); + regs.config_changed.store(true, Ordering::Release); + regs.consume_config_change(); + assert_eq!(regs.config_generation.load(Ordering::Acquire), 0x11); + regs.consume_config_change(); + assert_eq!(regs.config_generation.load(Ordering::Acquire), 0x11); + } }