riscv64: add interrupt support for net devices

Add interrupt support for VirtIO net devices on riscv64. This follows
the logic used for VirtIO block devices, inserting interrupts via the
`KVM_IRQ_LINE` ioctl.

Signed-off-by: Dimitris Charisis <dchar@cslab.ece.ntua.gr>

Author: Dimitris Charisis

src/vmm/src/builder.rs

@@ -54,7 +54,6 @@ use crate::devices::virtio::balloon::Balloon;
 use crate::devices::virtio::block::device::Block;
 use crate::devices::virtio::device::VirtioDevice;
 use crate::devices::virtio::mmio::MmioTransport;
-#[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
 use crate::devices::virtio::net::Net;
 #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
 use crate::devices::virtio::rng::Entropy;
@@ -291,7 +290,6 @@ pub fn build_microvm_for_boot(
         event_manager,
     )?;
 
-    #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
     attach_net_devices(
         &mut vmm,
         &mut boot_cmdline,
@@ -847,7 +845,6 @@ fn attach_block_devices<'a, I: Iterator<Item = &'a Arc<Mutex<Block>>> + Debug>(
     Ok(())
 }
 
-#[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
 fn attach_net_devices<'a, I: Iterator<Item = &'a Arc<Mutex<Net>>> + Debug>(
     vmm: &mut Vmm,
     cmdline: &mut LoaderKernelCmdline,

src/vmm/src/devices/virtio/net/device.rs

@@ -968,7 +968,7 @@ impl VirtioDevice for Net {
 
     #[cfg(target_arch = "riscv64")]
     fn interrupt_trigger_mut(&mut self) -> &mut IrqTrigger {
-        unimplemented!()
+        &mut self.irq_trigger
     }
 
     fn read_config(&self, offset: u64, data: &mut [u8]) {