pci: Make self mutable when reading from PCI config space

In order to anticipate the need to support more features related to the
access of a device's PCI config space, this commits changes the self
reference in the function read_config_register() to be mutable.

This also brings some more flexibility for any implementation of the
PciDevice trait.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

pci/src/bus.rs

@@ -67,7 +67,7 @@ impl PciDevice for PciRoot {
         self.config.write_config_register(reg_idx, offset, data);
     }
 
-    fn read_config_register(&self, reg_idx: usize) -> u32 {
+    fn read_config_register(&mut self, reg_idx: usize) -> u32 {
         self.config.read_reg(reg_idx)
     }
 

pci/src/device.rs

@@ -61,7 +61,7 @@ pub trait PciDevice: BusDevice {
     fn write_config_register(&mut self, reg_idx: usize, offset: u64, data: &[u8]);
     /// Gets a register from the configuration space.
     /// * `reg_idx` - The index of the config register to read.
-    fn read_config_register(&self, reg_idx: usize) -> u32;
+    fn read_config_register(&mut self, reg_idx: usize) -> u32;
     /// Detects if a BAR is being reprogrammed.
     fn detect_bar_reprogramming(
         &mut self,

vfio/src/vfio_pci.rs

@@ -852,7 +852,7 @@ impl PciDevice for VfioPciDevice {
             .region_write(VFIO_PCI_CONFIG_REGION_INDEX, data, reg + offset);
     }
 
-    fn read_config_register(&self, reg_idx: usize) -> u32 {
+    fn read_config_register(&mut self, reg_idx: usize) -> u32 {
         // When reading the BARs, we trap it and return what comes
         // from our local configuration space. We want the guest to
         // use that and not the VFIO device BARs as it does not map

vm-virtio/src/transport/pci_device.rs

@@ -556,7 +556,7 @@ impl PciDevice for VirtioPciDevice {
             .write_config_register(reg_idx, offset, data);
     }
 
-    fn read_config_register(&self, reg_idx: usize) -> u32 {
+    fn read_config_register(&mut self, reg_idx: usize) -> u32 {
         self.configuration.read_reg(reg_idx)
     }