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fix(virtio/pci): use volatile accesses for device features #1146

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Apr 20, 2024
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fix(virtio/pci): use volatile accesses for device features #1146

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10 changes: 6 additions & 4 deletions src/drivers/virtio/transport/pci.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -525,22 +525,24 @@ impl ComCfg {

/// Returns the features offered by the device. Coded in a 64bit value.
pub fn dev_features(&mut self) -> u64 {
let device_feature_select = ptr::from_mut(&mut self.com_cfg.device_feature_select);
let device_feature = ptr::from_mut(&mut self.com_cfg.device_feature);
// Indicate device to show high 32 bits in device_feature field.
// See Virtio specification v1.1. - 4.1.4.3
memory_barrier();
self.com_cfg.device_feature_select = 1;
unsafe { device_feature_select.write_volatile(1) };
memory_barrier();

// read high 32 bits of device features
let mut dev_feat = u64::from(self.com_cfg.device_feature) << 32;
let mut dev_feat = u64::from(unsafe { device_feature.read_volatile() }) << 32;

// Indicate device to show low 32 bits in device_feature field.
// See Virtio specification v1.1. - 4.1.4.3
self.com_cfg.device_feature_select = 0;
unsafe { device_feature_select.write_volatile(0) };
memory_barrier();

// read low 32 bits of device features
dev_feat |= u64::from(self.com_cfg.device_feature);
dev_feat |= u64::from(unsafe { device_feature.read_volatile() });

dev_feat
}
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