Re: [Buildroot] [PATCH] support/testing: test_xen: add networking

["Vincent Stehlé" <vincent.stehle@arm.com>]

On Sat, Oct 11, 2025 at 10:35:07PM +0200, Julien Olivain wrote:
> Hi Vincent,
> 
> Thanks for the patch.
> 
> On 10/10/2025 09:29, Vincent Stehlé wrote:
> > Enhance the Xen python tests to exercise networking:
> > 
> > - Add the networking support we need to the Linux kernel configurations.
> > - Add a virtual network interface to the Xen dom1 configurations.
> > - Update the test in the following way:
> >   * Start the emulator with restricted networking.
> >   * Create a network bridge in dom0.
> >   * Check that networking is functional in both domains by ping'ing the
> >     gateway.
> >   (Refer also to the diagram in the python script.)
> > - While at it, bump Linux kernel to 6.17.1 and U-Boot to 2025.07.
> >   We also need to adjust the DTB address in the Arm 32b U-Boot script to
> >   accommodate the new U-Boot version, which does not have enough free
> > space
> >   around the control DTB anymore.
> > 
> > Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>
> 
> For some reason, the TestXenArmv7 runtime test is failing in the
> reference Buildroot Docker image. I tested with the command:
> 
>     utils/docker-run support/testing/run-tests \
>         -k -d dl -o output_folder \
>         tests.package.test_xen
> 
> The file output_folder/TestXenArmv7-run.log ends with:
> 
> 	[BRTEST# udhcpc -i eth0
> 	udhcpc: started, v1.37.0
> 	udhcpc: broadcasting discover
> 	udhcpc: broadcasting discover

Hi Julien,

Good catch! I thought I did test this, but maybe not the last version with guest
ping, sorry :(

> 
> Strangely, the TestXenAarch64 is passing in the Build Docker image.
> 
> I initially thought it was a timing issue, but I tested several times
> and I consistently got the same result.
> 
> Both tests are passing on a Fedora 42 host with qemu 9.2.4.
> 
> The Buildroot Docker image has an "old" qemu 7.2.15. See the command:
> 
>     utils/docker-run qemu-system-arm --version
> 
> which output:
> 
>     QEMU emulator version 7.2.15 (Debian 1:7.2+dfsg-7+deb12u12)

It seems that Qemu versions <= 9.0.4 break the test, and >= 9.1.0 repair it.
Whatever the reason, I will try to make the test pass on gitlab and send a v2.

Best regards,
Vincent.

> 
> I tested by adding in the test config:
> 
>     BR2_PACKAGE_HOST_QEMU=y
>     BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y
> 
> in order to compile a more recent qemu 10.1.0. This seems to
> solve or workaround the issue.
> 
> For the moment, I cannot tell if it's a network emulation bug in
> the old qemu (which in that case the test needs to compile the newer
> qemu), or if it's a timing issue in the test (i.e. the test
> might need to wait a bit somewhere to let the bridge settle).
> 
> Could you have a look please and send an updated patch addressing
> this issue, please?
> 
> Best regards,
> 
> Julien.
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