devices: Extend the Bus trait to carry the device range base

With the range base for the IO/MMIO vm exit address, a device with
multiple ranges has all the needed information for resolving which of
its range the exit is coming from

Fixes: #87

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

devices/src/bus.rs

@@ -19,9 +19,9 @@ use std::sync::{Arc, Mutex};
 #[allow(unused_variables)]
 pub trait BusDevice: Send {
     /// Reads at `offset` from this device
-    fn read(&mut self, offset: u64, data: &mut [u8]) {}
+    fn read(&mut self, base: u64, offset: u64, data: &mut [u8]) {}
     /// Writes at `offset` into this device
-    fn write(&mut self, offset: u64, data: &[u8]) {}
+    fn write(&mut self, base: u64, offset: u64, data: &[u8]) {}
     /// Triggers the `irq_mask` interrupt on this device
     fn interrupt(&self, irq_mask: u32) {}
 }
@@ -137,11 +137,11 @@ impl Bus {
     ///
     /// Returns true on success, otherwise `data` is untouched.
     pub fn read(&self, addr: u64, data: &mut [u8]) -> bool {
-        if let Some((_base, offset, dev)) = self.resolve(addr) {
+        if let Some((base, offset, dev)) = self.resolve(addr) {
             // OK to unwrap as lock() failing is a serious error condition and should panic.
             dev.lock()
                 .expect("Failed to acquire device lock")
-                .read(offset, data);
+                .read(base, offset, data);
             true
         } else {
             false
@@ -152,11 +152,11 @@ impl Bus {
     ///
     /// Returns true on success, otherwise `data` is untouched.
     pub fn write(&self, addr: u64, data: &[u8]) -> bool {
-        if let Some((_base, offset, dev)) = self.resolve(addr) {
+        if let Some((base, offset, dev)) = self.resolve(addr) {
             // OK to unwrap as lock() failing is a serious error condition and should panic.
             dev.lock()
                 .expect("Failed to acquire device lock")
-                .write(offset, data);
+                .write(base, offset, data);
             true
         } else {
             false