On 12/30/25 16:45, Manjae Cho wrote:
Add network testing documentation for QEMU emulation based on actual
runtime testing with qemu-system-riscv64 and U-Boot.
Tested and verified:
- VirtIO network device detection (virtio-net-device)
- DHCP client functionality
- TFTP file loading from QEMU's built-in TFTP server
The documentation covers VirtIO devices for both MMIO-based (RISC-V)
and PCI-based (x86) machines, with practical examples of U-Boot commands
and expected output.
In the meantime I sent
[PATCH 1/1] doc: describe QEMU networking
https://lore.kernel.org/u-boot/[email protected]/
Did you have a chance to look at it?
Signed-off-by: Manjae Cho <[email protected]>
---
doc/board/emulation/index.rst | 1 +
doc/board/emulation/network.rst | 58 +++++++++++++++++++++++++++++++++
2 files changed, 59 insertions(+)
create mode 100644 doc/board/emulation/network.rst
diff --git a/doc/board/emulation/index.rst b/doc/board/emulation/index.rst
index f8908166276..507c38825c1 100644
--- a/doc/board/emulation/index.rst
+++ b/doc/board/emulation/index.rst
@@ -8,6 +8,7 @@ Emulation
acpi
blkdev
+ index
qemu-arm
qemu-mips
qemu-ppce500
diff --git a/doc/board/emulation/network.rst b/doc/board/emulation/network.rst
new file mode 100644
index 00000000000..6a08a6611b4
--- /dev/null
+++ b/doc/board/emulation/network.rst
@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0+
.. SPDX-License-Identifier: GPL-2.0-or-later
see https://spdx.org/licenses/GPL-2.0-or-later.html
+
+Emulation of network devices
+-----------------------------
+
+QEMU can emulate network devices for testing U-Boot networking functionality.
+The device type depends on the machine architecture:
+
+* VirtIO (for RISC-V and other virtio-bus machines)
RISC-V also supports PCI. For productive use the important message is
that virtio-net provides the fastest emulation by hardware emulation.
+
+ .. code-block:: bash
+
+ qemu-system-riscv64 -nographic -machine virt -bios opensbi.bin \
+ -kernel u-boot.bin -m 256M \
+ -netdev user,id=net0 -device virtio-net-device,netdev=net0
+
+* VirtIO PCI (for x86 and other PCI-based machines)
+
+ .. code-block:: bash
+
+ qemu-system-x86_64 -nographic -bios u-boot.bin \
+ -netdev user,id=net0 -device virtio-net-pci,netdev=net0
+
+The 'user' networking backend provides a simple way to test DHCP and basic
+networking without host configuration. In U-Boot, you can verify the network
+device is detected:
+
+.. code-block:: none
+
+ => net list
+ eth0 : virtio-net#0 52:54:00:12:34:56 active
+
+TFTP boot
+^^^^^^^^^
TFTP boot is disabled via `setenv autoload no`. The heading seems not to
match the content of the section.
The dhcp, net, and tftpboot commands should be documented in
doc/usage/cmd/. But mentioning them here looks ok to me.
Best regards
Heinrich
+
+QEMU's user networking includes a built-in TFTP server. To enable it, specify
+a host directory to serve files from:
+
+.. code-block:: bash
+
+ -netdev user,id=net0,tftp=/path/to/tftp/root
+
+From U-Boot, you can load files using DHCP and TFTP:
+
+.. code-block:: none
+
+ => setenv autoload no
+ => dhcp
+ DHCP client bound to address 10.0.2.15 (1 ms)
+ => tftp ${loadaddr} test.txt
+ Using virtio-net#0 device
+ TFTP from server 10.0.2.2; our IP address is 10.0.2.15
+ Filename 'test.txt'.
+ Load address: 0x80200000
+ Loading: *
+ 15.6 KiB/s
+ done
+ Bytes transferred = 16 (10 hex)
