sysprog21 · otischung · Jun 30, 2025 · Jun 30, 2025 · jserv · Jul 4, 2025
diff --git a/README.md b/README.md
@@ -33,6 +33,8 @@ make check
 
 ## Usage
 
+### Start Emulator
+
 ```
 build/kvm-host -k bzImage [-i initrd] [-d disk-image]
 ```
@@ -42,8 +44,63 @@ containing concatenated `bootsect.o + setup.o + misc.o + piggy.o`. `initrd` is t
 initial RAM disk image, which is an optional argument.
 `disk-image` is the path to disk image which can be mounted as a block device via virtio. For the reference Linux guest, ext4 filesystem is used for disk image.
 
+### Stop Emulator
+
 To exit kvm-host, press "Ctrl-A", release both keys, and then press "x".
 
+### Enable Static Route to Test the Guest VirtIO-Net Interface
+
+1. Start the kvm-host emulator. Once initialized, the TUN/TAP interface (for example, `tap0`) is visible in the output of `ip a`. The following is sample output from the host:
+
+   ```shell
+   ❯ ip a
+   1: lo: ...
+   2: eth0: ...
+   3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
+       link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
+       altname xxxxxxxxxxxxxxx
+       inet 192.168.x.x/24 brd 192.168.x.255 scope global dynamic noprefixroute wlan0
+          valid_lft xxxxxxsec preferred_lft xxxxxxsec
+       inet6 ...
+   11: tap0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
+       link/ether 5a:1d:bd:2d:7c:1f brd ff:ff:ff:ff:ff:ff
+   ```
+
+2. Execute the shell script `./scripts/set-host-bridge.sh`, which configures a bridge by assigning the default route to 10.0.0.1, integrating the TUN/TAP interface into the bridge, and activating the network interfaces. The following is sample output of `ip a` from the host:
+
+   ```shell
+   ❯ ip a
+   ...
+   11: tap0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
+       link/ether 5a:1d:bd:2d:7c:1f brd ff:ff:ff:ff:ff:ff
+   12: br0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
+       link/ether d6:92:97:85:e8:7c brd ff:ff:ff:ff:ff:ff
+       inet 10.0.0.1/24 scope global br0
+          valid_lft forever preferred_lft forever
+   ```
+
+3. Copy the commands from `scripts/set-guest-route.sh` into the guest environment and execute them. Below is a sample `ip a` output from the guest:
+
+   ```shell
+   ~ # ip a
+   1: lo: <LOOPBACK> mtu 65536 qdisc noop qlen 1000
+       link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+   2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
+       link/ether c2:5a:92:87:97:42 brd ff:ff:ff:ff:ff:ff
+       inet 10.0.0.2/24 scope global eth0
+          valid_lft forever preferred_lft forever
+       inet6 fe80::c05a:92ff:fe87:9742/64 scope link 
+          valid_lft forever preferred_lft forever
+   3: sit0@NONE: <NOARP> mtu 1480 qdisc noop qlen 1000
+       link/sit 0.0.0.0 brd 0.0.0.0
+   ```
+
+4. Test guest network connectivity by pinging the configured default gateway.
+
+   ```bash
+   ping 10.0.0.1
+   ```
+
 ## License
 
 `kvm-host` is released under the BSD 2 clause license. Use of this source code is governed by
@@ -52,7 +109,7 @@ a BSD-style license that can be found in the LICENSE file.
 ## References
 * [kvmtool](https://github.com/kvmtool/kvmtool)
 * [KVM (Kernel-based Virtual Machine) API](https://www.kernel.org/doc/Documentation/virtual/kvm/api.txt)
-* [The Linux/x86 Boot Protocol](https://www.kernel.org/doc/html/latest/x86/boot.html)
+* [The Linux/x86 Boot Protocol](https://www.kernel.org/doc/html/latest/arch/x86/boot.html)
 * [Using the KVM API](https://lwn.net/Articles/658511/)
 * [gokvm](https://github.com/bobuhiro11/gokvm)
 * [KVM Host in a few lines of code](https://zserge.com/posts/kvm/)

diff --git a/configs/linux-arm64.config b/configs/linux-arm64.config
@@ -12,7 +12,7 @@ CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 # CONFIG_MULTIUSER is not set
 # CONFIG_SYSFS_SYSCALL is not set
 # CONFIG_FHANDLE is not set
-# CONFIG_POSIX_TIMERS is not set
+CONFIG_POSIX_TIMERS=y
 # CONFIG_BUG is not set
 # CONFIG_BASE_FULL is not set
 # CONFIG_FUTEX is not set
@@ -66,3 +66,15 @@ CONFIG_EXT4_FS=y
 # CONFIG_DEBUG_MISC is not set
 # CONFIG_FTRACE is not set
 # CONFIG_STRICT_DEVMEM is not set
+CONFIG_NET=y
+CONFIG_INET=y
+CONFIG_IP_MULTICAST=y
+CONFIG_IP_PNP=y
+CONFIG_IP_PNP_DHCP=y
+CONFIG_NETDEVICES=y
+CONFIG_VIRTIO=y
+CONFIG_VIRTIO_NET=y
+CONFIG_VIRTIO_RING=y
+CONFIG_UNIX=y
+CONFIG_UNIX_SCM=y
+CONFIG_AF_UNIX_OOB=y
diff --git a/scripts/set-guest-route.sh b/scripts/set-guest-route.sh
@@ -0,0 +1,3 @@
+ip addr add 10.0.0.2/24 dev eth0
+ip link set eth0 up
+ip route add default via 10.0.0.1
diff --git a/scripts/set-host-bridge.sh b/scripts/set-host-bridge.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+sudo ip link delete br0 || true
+sudo brctl addbr br0
+sudo ip addr add 10.0.0.1/24 dev br0
+sudo ip route add default via 10.0.0.1 dev br0
+sudo ip link set br0 up
+sudo ip link set tap0 master br0
+sudo ip link set tap0 up
diff --git a/src/arch/arm64/desc.h b/src/arch/arm64/desc.h
@@ -3,4 +3,5 @@
 #define RAM_BASE (1UL << 31)
 #define SERIAL_IRQ 0
 #define VIRTIO_BLK_IRQ 1
+#define VIRTIO_NET_IRQ 2
 #define KERNEL_OPTS "console=ttyS0"
diff --git a/src/arch/arm64/vm.c b/src/arch/arm64/vm.c
@@ -378,10 +378,12 @@ static int generate_fdt(vm_t *v)
     __FDT(property, "ranges", &pci_ranges, sizeof(pci_ranges));
     /* interrupt-map contains the interrupt mapping between the PCI device and
      * the IRQ number of interrupt controller.
-     * virtio-blk is the only PCI device.
+     * interrupt-map: map each PCI device’s INTA#: GIC SPI
      */
     struct virtio_blk_dev *virtio_blk = &v->virtio_blk_dev;
     struct pci_dev *virtio_blk_pci = (struct pci_dev *) virtio_blk;
+    struct virtio_net_dev *virtio_net = &v->virtio_net_dev;
+    struct pci_dev *virtio_net_pci = (struct pci_dev *) virtio_net;
     struct {
         uint32_t pci_hi;
         uint64_t pci_addr;
@@ -390,15 +392,28 @@ static int generate_fdt(vm_t *v)
         uint32_t gic_type;
         uint32_t gic_irqn;
         uint32_t gic_irq_type;
-    } __attribute__((packed)) pci_irq_map[] = {{
-        cpu_to_fdt32(virtio_blk_pci->config_dev.base & ~(1UL << 31)),
-        0,
-        cpu_to_fdt32(1),
-        cpu_to_fdt32(FDT_PHANDLE_GIC),
-        cpu_to_fdt32(ARM_FDT_IRQ_TYPE_SPI),
-        cpu_to_fdt32(VIRTIO_BLK_IRQ),
-        cpu_to_fdt32(ARM_FDT_IRQ_EDGE_TRIGGER),
-    }};
+    } __attribute__((packed)) pci_irq_map[] = {
+        /* virtio-blk: SPI VIRTIO_BLK_IRQ */
+        {
+            cpu_to_fdt32(virtio_blk_pci->config_dev.base & ~(1UL << 31)),
+            0,
+            cpu_to_fdt32(1),
+            cpu_to_fdt32(FDT_PHANDLE_GIC),
+            cpu_to_fdt32(ARM_FDT_IRQ_TYPE_SPI),
+            cpu_to_fdt32(VIRTIO_BLK_IRQ),
+            cpu_to_fdt32(ARM_FDT_IRQ_EDGE_TRIGGER),
+        },
+        /* virtio-net: SPI VIRTIO_NET_IRQ */
+        {
+            cpu_to_fdt32(virtio_net_pci->config_dev.base & ~(1UL << 31)),
+            0,
+            cpu_to_fdt32(1),
+            cpu_to_fdt32(FDT_PHANDLE_GIC),
+            cpu_to_fdt32(ARM_FDT_IRQ_TYPE_SPI),
+            cpu_to_fdt32(VIRTIO_NET_IRQ),
+            cpu_to_fdt32(ARM_FDT_IRQ_EDGE_TRIGGER),
+        },
+    };
     __FDT(property, "interrupt-map", &pci_irq_map, sizeof(pci_irq_map));
     __FDT(end_node); /* End of /pci node */