From 21bd3ae91661104a7c58662316b4538eac09fbc7 Mon Sep 17 00:00:00 2001
From: Peter Oskolkov <posk@google.com>
Date: Thu, 12 Mar 2026 09:51:50 -0700
Subject: [PATCH] virtio-devices: switch driver_status to Arc<AtomicU8>

Signed-off-by: Peter Oskolkov <posk@google.com>
---
 virtio-devices/src/transport/pci_common_config.rs | 14 +++++++-------
 virtio-devices/src/transport/pci_device.rs        | 10 ++++++----
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/virtio-devices/src/transport/pci_common_config.rs b/virtio-devices/src/transport/pci_common_config.rs
index 68ed01c60..dcd65f7bc 100644
--- a/virtio-devices/src/transport/pci_common_config.rs
+++ b/virtio-devices/src/transport/pci_common_config.rs
@@ -6,7 +6,7 @@
 //
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
 
-use std::sync::atomic::{AtomicU16, Ordering};
+use std::sync::atomic::{AtomicU8, AtomicU16, Ordering};
 use std::sync::{Arc, Mutex};
 
 use byteorder::{ByteOrder, LittleEndian};
@@ -125,7 +125,7 @@ pub fn get_vring_size(t: VringType, queue_size: u16) -> u64 {
 ///    le64 queue_used;                // 0x30 // read-write
 pub struct VirtioPciCommonConfig {
     pub access_platform: Option<Arc<dyn AccessPlatform>>,
-    pub driver_status: u8,
+    pub driver_status: Arc<AtomicU8>,
     pub config_generation: u8,
     pub device_feature_select: u32,
     pub driver_feature_select: u32,
@@ -141,7 +141,7 @@ impl VirtioPciCommonConfig {
     ) -> Self {
         VirtioPciCommonConfig {
             access_platform,
-            driver_status: state.driver_status,
+            driver_status: Arc::new(AtomicU8::new(state.driver_status)),
             config_generation: state.config_generation,
             device_feature_select: state.device_feature_select,
             driver_feature_select: state.driver_feature_select,
@@ -153,7 +153,7 @@ impl VirtioPciCommonConfig {
 
     fn state(&self) -> VirtioPciCommonConfigState {
         VirtioPciCommonConfigState {
-            driver_status: self.driver_status,
+            driver_status: self.driver_status.load(Ordering::Acquire),
             config_generation: self.config_generation,
             device_feature_select: self.device_feature_select,
             driver_feature_select: self.driver_feature_select,
@@ -223,7 +223,7 @@ impl VirtioPciCommonConfig {
         debug!("read_common_config_byte: offset 0x{offset:x}");
         // The driver is only allowed to do aligned, properly sized access.
         match offset {
-            0x14 => self.driver_status,
+            0x14 => self.driver_status.load(Ordering::Acquire),
             0x15 => self.config_generation,
             _ => {
                 warn!("invalid virtio config byte read: 0x{offset:x}");
@@ -235,7 +235,7 @@ impl VirtioPciCommonConfig {
     fn write_common_config_byte(&mut self, offset: u64, value: u8) {
         debug!("write_common_config_byte: offset 0x{offset:x}");
         match offset {
-            0x14 => self.driver_status = value,
+            0x14 => self.driver_status.store(value, Ordering::Release),
             _ => {
                 warn!("invalid virtio config byte write: 0x{offset:x}");
             }
@@ -437,7 +437,7 @@ mod unit_tests {
     fn write_base_regs() {
         let mut regs = VirtioPciCommonConfig {
             access_platform: None,
-            driver_status: 0xaa,
+            driver_status: Arc::new(AtomicU8::new(0xaa)),
             config_generation: 0x55,
             device_feature_select: 0x0,
             driver_feature_select: 0x0,
diff --git a/virtio-devices/src/transport/pci_device.rs b/virtio-devices/src/transport/pci_device.rs
index 26440ddf2..1a8d3da96 100644
--- a/virtio-devices/src/transport/pci_device.rs
+++ b/virtio-devices/src/transport/pci_device.rs
@@ -660,13 +660,13 @@ impl VirtioPciDevice {
     fn is_driver_ready(&self) -> bool {
         let ready_bits =
             (DEVICE_ACKNOWLEDGE | DEVICE_DRIVER | DEVICE_DRIVER_OK | DEVICE_FEATURES_OK) as u8;
-        self.common_config.driver_status == ready_bits
-            && self.common_config.driver_status & DEVICE_FAILED as u8 == 0
+        let driver_status = self.common_config.driver_status.load(Ordering::SeqCst);
+        driver_status == ready_bits && (driver_status & DEVICE_FAILED as u8) == 0
     }
 
     /// Determines if the driver has requested the device (re)init / reset itself
     fn is_driver_init(&self) -> bool {
-        self.common_config.driver_status == DEVICE_INIT as u8
+        self.common_config.driver_status.load(Ordering::SeqCst) == DEVICE_INIT as u8
     }
 
     pub fn config_bar_addr(&self) -> u64 {
@@ -1238,7 +1238,9 @@ impl PciDevice for VirtioPciDevice {
                 self.common_config.queue_select = 0;
             } else {
                 error!("Attempt to reset device when not implemented in underlying device");
-                self.common_config.driver_status = crate::DEVICE_FAILED as u8;
+                self.common_config
+                    .driver_status
+                    .store(crate::DEVICE_FAILED as u8, Ordering::SeqCst);
             }
         }