diff --git a/devices/src/pci/mod.rs b/devices/src/pci/mod.rs
index 071930dede..d997af039e 100644
--- a/devices/src/pci/mod.rs
+++ b/devices/src/pci/mod.rs
@@ -4,6 +4,8 @@
 
 //! Implements pci devices and busses.
 
+mod pci_configuration;
+
 /// PCI has four interrupt pins A->D.
 #[derive(Copy, Clone)]
 pub enum PciInterruptPin {
diff --git a/devices/src/pci/pci_configuration.rs b/devices/src/pci/pci_configuration.rs
new file mode 100644
index 0000000000..4b4c4274ad
--- /dev/null
+++ b/devices/src/pci/pci_configuration.rs
@@ -0,0 +1,240 @@
+// Copyright 2018 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+use pci::PciInterruptPin;
+
+// The number of 32bit registers in the config space, 256 bytes.
+const NUM_CONFIGURATION_REGISTERS: usize = 64;
+
+const BAR0_REG: usize = 4;
+const BAR_IO_ADDR_MASK: u32 = 0xffff_fffc;
+const BAR_IO_BIT: u32 = 0x0000_0001;
+const BAR_MEM_ADDR_MASK: u32 = 0xffff_fff0;
+const NUM_BAR_REGS: usize = 6;
+
+const INTERRUPT_LINE_PIN_REG: usize = 15;
+
+/// Represents the types of PCI headers allowed in the configuration registers.
+#[derive(Copy, Clone)]
+pub enum PciHeaderType {
+    Device,
+    Bridge,
+}
+
+/// Classes of PCI nodes.
+#[allow(dead_code)]
+#[derive(Copy, Clone)]
+pub enum PciClassCode {
+    TooOld,
+    MassStorage,
+    NetworkController,
+    DisplayController,
+    MultimediaController,
+    MemoryController,
+    BridgeDevice,
+    SimpleCommunicationController,
+    BaseSystemPeripheral,
+    InputDevice,
+    DockingStation,
+    Processor,
+    SerialBusController,
+    WirelessController,
+    IntelligentIoController,
+    EncryptionController,
+    DataAcquisitionSignalProcessing,
+    Other = 0xff,
+}
+
+impl PciClassCode {
+    pub fn get_register_value(&self) -> u8 {
+        *self as u8
+    }
+}
+
+/// A PCI sublcass. Each class in `PciClassCode` can specify a unique set of subclasses. This trait
+/// is implemented by each subclass. It allows use of a trait object to generate configurations.
+pub trait PciSubclass {
+    /// Convert this subclass to the value used in the PCI specification.
+    fn get_register_value(&self) -> u8;
+}
+
+/// Subclasses of the MultimediaController class.
+#[allow(dead_code)]
+#[derive(Copy, Clone)]
+pub enum PciMultimediaSubclass {
+    VideoController = 0x00,
+    AudioController = 0x01,
+    TelephonyDevice = 0x02,
+    AudioDevice = 0x03,
+    Other = 0x80,
+}
+
+impl PciSubclass for PciMultimediaSubclass {
+    fn get_register_value(&self) -> u8 {
+        *self as u8
+    }
+}
+
+/// Subclasses of the BridgeDevice
+#[allow(dead_code)]
+#[derive(Copy, Clone)]
+pub enum PciBridgeSubclass {
+    HostBridge = 0x00,
+    IsaBridge = 0x01,
+    EisaBridge = 0x02,
+    McaBridge = 0x03,
+    PciToPciBridge = 0x04,
+    PcmciaBridge = 0x05,
+    NuBusBridge = 0x06,
+    CardBusBridge = 0x07,
+    RACEwayBridge = 0x08,
+    PciToPciSemiTransparentBridge = 0x09,
+    InfiniBrandToPciHostBridge = 0x0a,
+    OtherBridgeDevice = 0x80,
+}
+
+impl PciSubclass for PciBridgeSubclass {
+    fn get_register_value(&self) -> u8 {
+        *self as u8
+    }
+}
+
+/// Contains the configuration space of a PCI node.
+/// See the [specification](https://en.wikipedia.org/wiki/PCI_configuration_space).
+/// The configuration space is accessed with DWORD reads and writes from the guest.
+pub struct PciConfiguration {
+    registers: [u32; NUM_CONFIGURATION_REGISTERS],
+    writable_bits: [u32; NUM_CONFIGURATION_REGISTERS], // writable bits for each register.
+    num_bars: usize,
+}
+
+impl PciConfiguration {
+    pub fn new(
+        vendor_id: u16,
+        device_id: u16,
+        class_code: PciClassCode,
+        subclass: &PciSubclass,
+        header_type: PciHeaderType,
+    ) -> Self {
+        let mut registers = [0u32; NUM_CONFIGURATION_REGISTERS];
+        registers[0] = u32::from(device_id) << 16 | u32::from(vendor_id);
+        registers[2] = u32::from(class_code.get_register_value()) << 24
+            | u32::from(subclass.get_register_value()) << 16;
+        match header_type {
+            PciHeaderType::Device => (),
+            PciHeaderType::Bridge => registers[3] = 0x0001_0000,
+        };
+        PciConfiguration {
+            registers,
+            writable_bits: [0xffff_ffff; NUM_CONFIGURATION_REGISTERS],
+            num_bars: 0,
+        }
+    }
+
+    /// Reads a 32bit register from `reg_idx` in the register map.
+    pub fn read_reg(&self, reg_idx: usize) -> u32 {
+        *(self.registers.get(reg_idx).unwrap_or(&0xffff_ffff))
+    }
+
+    /// Writes a 32bit register to `reg_idx` in the register map.
+    pub fn write_reg(&mut self, reg_idx: usize, value: u32) {
+        if let Some(r) = self.registers.get_mut(reg_idx) {
+            *r = value & self.writable_bits[reg_idx];
+        } else {
+            warn!("bad PCI register write {}", reg_idx);
+        }
+    }
+
+    /// Writes a 16bit word to `offset`. `offset` must be 16bit aligned.
+    pub fn write_word(&mut self, offset: usize, value: u16) {
+        let shift = match offset % 4 {
+            0 => 0,
+            2 => 16,
+            _ => {
+                warn!("bad PCI config write offset {}", offset);
+                return;
+            }
+        };
+        let reg_idx = offset / 4;
+
+        if let Some(r) = self.registers.get_mut(reg_idx) {
+            let writable_mask = self.writable_bits[reg_idx];
+            let mask = (0xffffu32 << shift) & writable_mask;
+            let shifted_value = (u32::from(value) << shift) & writable_mask;
+            *r = *r & !mask | shifted_value;
+        } else {
+            warn!("bad PCI config write offset {}", offset);
+        }
+    }
+
+    /// Writes a byte to `offset`.
+    pub fn write_byte(&mut self, offset: usize, value: u8) {
+        let shift = (offset % 4) * 8;
+        let reg_idx = offset / 4;
+
+        if let Some(r) = self.registers.get_mut(reg_idx) {
+            let writable_mask = self.writable_bits[reg_idx];
+            let mask = (0xffu32 << shift) & writable_mask;
+            let shifted_value = (u32::from(value) << shift) & writable_mask;
+            *r = *r & !mask | shifted_value;
+        } else {
+            warn!("bad PCI config write offset {}", offset);
+        }
+    }
+
+    // Add either an IO or memory region, depending on `mem_type` mask, which is ORed in to the
+    // value before saving it.
+    fn add_bar(&mut self, addr: u64, size: u64, addr_mask: u32, mem_type: u32) -> Option<usize> {
+        if self.num_bars >= NUM_BAR_REGS {
+            return None;
+        }
+        if size.count_ones() != 1 {
+            return None;
+        }
+
+        // TODO(dgreid) Allow 64 bit address and size.
+        if addr.checked_add(size)? > u64::from(u32::max_value()) {
+                return None;
+        }
+
+        let bar_idx = BAR0_REG + self.num_bars;
+
+        self.registers[bar_idx] = addr as u32 & addr_mask | mem_type;
+        // The first writable bit represents the size of the region.
+        self.writable_bits[bar_idx] = !(size - 1) as u32;
+
+        self.num_bars += 1;
+        Some(bar_idx)
+    }
+
+    /// Adds a memory region of `size` at `addr`. Configures the next available BAR register to
+    /// report this region and size to the guest kernel. Returns 'None' if all BARs are full, or
+    /// `Some(BarIndex)` on success. `size` must be a power of 2.
+    pub fn add_memory_region(&mut self, addr: u64, size: u64) -> Option<usize> {
+        self.add_bar(addr, size, BAR_MEM_ADDR_MASK, 0)
+    }
+
+    /// Adds an IO region of `size` at `addr`. Configures the next available BAR register to
+    /// report this region and size to the guest kernel. Returns 'None' if all BARs are full, or
+    /// `Some(BarIndex)` on success. `size` must be a power of 2.
+    pub fn add_io_region(&mut self, addr: u64, size: u64) -> Option<usize> {
+        self.add_bar(addr, size, BAR_IO_ADDR_MASK, BAR_IO_BIT)
+    }
+
+    /// Returns the address of the given BAR region.
+    pub fn get_bar_addr(&self, bar_num: usize) -> u32 {
+        let bar_idx = BAR0_REG + bar_num;
+
+        self.registers[bar_idx] & BAR_MEM_ADDR_MASK
+    }
+
+    /// Configures the IRQ line and pin used by this device.
+    pub fn set_irq(&mut self, line: u8, pin: PciInterruptPin) {
+        // `pin` is 1-based in the pci config space.
+        let pin_idx = (pin as u32) + 1;
+        self.registers[INTERRUPT_LINE_PIN_REG] = (self.registers[INTERRUPT_LINE_PIN_REG]
+            & 0xffff_0000) | (pin_idx << 8)
+            | u32::from(line);
+    }
+}