feat: only map GICD regs once

kernel/src/arch/aarch64/irq/gic/mod.rs

@@ -4,7 +4,7 @@ use crate::dev::{
     irq::{IntController, IntSource, IrqContext},
     Device,
 };
-use crate::mem::virt::DeviceMemoryIo;
+use crate::mem::virt::{DeviceMemoryIo, DeviceMemory};
 use crate::sync::IrqSafeNullLock;
 use crate::util::InitOnce;
 use error::Errno;
@@ -52,10 +52,9 @@ impl Device for Gic {
     }
 
     unsafe fn enable(&self) -> Result<(), Errno> {
-        let gicd_mmio_shared =
-            DeviceMemoryIo::map("GICv2 shared Distributor registers", self.gicd_base, 1)?;
-        let gicd_mmio_banked =
-            DeviceMemoryIo::map("GICv2 banked Distributor registers", self.gicd_base, 1)?;
+        let gicd_mmio = DeviceMemory::map("GICv2 Distributor registers", self.gicd_base, 1)?;
+        let gicd_mmio_shared = DeviceMemoryIo::new(gicd_mmio.clone());
+        let gicd_mmio_banked = DeviceMemoryIo::new(gicd_mmio);
         let gicc_mmio = DeviceMemoryIo::map("GICv2 CPU registers", self.gicc_base, 1)?;
 
         let mut gicd = Gicd::new(gicd_mmio_shared, gicd_mmio_banked);

kernel/src/mem/virt/mod.rs

@@ -111,6 +111,15 @@ impl DeviceMemory {
 
         Ok(Self { name, base, count })
     }
+
+    pub unsafe fn clone(&self) -> Self {
+        // TODO maybe add refcount and remove "unsafe"?
+        Self {
+            name: self.name,
+            base: self.base,
+            count: self.count
+        }
+    }
 }
 
 impl<T> DeviceMemoryIo<T> {