feat: pci passthrough (#114)

* feat: pci passthrough

* feat: guest device management

* feat: addons mounting and kernel modules support

* feat: more pci work

* fix: kernel build squashfs fixes

* fix: e820entry should be available on all platforms

crates/xen/xenclient/examples/pci.rs

@@ -0,0 +1,32 @@
+use xenclient::pci::*;
+
+use xenclient::error::Result;
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let backend = XenPciBackend::new();
+    if !backend.is_loaded().await? {
+        return Err(xenclient::error::Error::GenericError(
+            "xen-pciback module not loaded".to_string(),
+        ));
+    }
+
+    println!("assignable devices:");
+    for device in backend.list_devices().await? {
+        let is_assigned = backend.is_assigned(&device).await?;
+        let has_slot = backend.has_slot(&device).await?;
+        println!("{} slot={} assigned={}", device, has_slot, is_assigned);
+        let resources = backend.read_resources(&device).await?;
+        for resource in resources {
+            println!(
+                "  resource start={:#x} end={:#x} flags={:#x} bar-io={}",
+                resource.start,
+                resource.end,
+                resource.flags,
+                resource.is_bar_io()
+            );
+        }
+    }
+
+    Ok(())
+}