Hello,
We are trying to boot Xen on a Samsung XE303C12 Chromebook aka "snow" following the suggestions in the slide show presentiation here:
https://www.slideshare.net/xen_com_mgr/xpds16-porting-xen-on-arm-to-a-new-soc-julien-grall-arm
This device uses an exynos5250 SOC dual core 1.7 GHz with 2 MB RAM, it is a Samsung armv7 chip with virtualization extensions.
In particular, we have it working fairly well both on the bare metal with a recent 6.1.59 Linux LTS kernel and also with a recent 5.4.257 LTS kernel with KVM, the older LTS kernel version is used to test KVM because support for KVM on arm v7 was removed from Linux around kernel version 5.7. So we know we have the hypervisor mode enabled because we were able to use it with KVM.
For Xen, we are using the latest Debian build of Xen 4.17 for the Debian armhf architecture:
(XEN) Xen version 4.17.2-pre (Debian 4.17.1+2-gb773c48e36-1) (pkg-xen-devel@lists.alioth.debian.org) (arm-linux-gnueabihf-gcc (Debian 12.2.0-14) 12.2.0) debug=n Thu May 18 19:26:30 UTC 2023
The Linux kernel is a custom build that adds the Xen config kernel options (CONFIG_XEN_DOM0, etc) on top of a kernel that works well on the same Chromebook model on the bare metal. I can provide the config options of the kernel that was used if that is helpful.
Out method of booting is to have u-boot boot the Xen hypervisor and load the device tree after adding the dom0 to the otherwise unaltered device tree from the Linux kernel using u-boot fdt commands to add a /chosen node, as described on the Xen wiki and in the pages linked from there. We have also tried adding and loading an initrd.img using the device tree /chosen node but that made no difference in our tests.
We actually have the Linux LTS kernel version 6.1.59 working as dom0 with Xen using the same version of u-boot that we used for KVM, but with a big problem.
The problem we see is that when booting the 6.1.59 kernel version as dom0 with Xen, the screen is totally dark and the only way to access the system is remotely through ssh. Logs indicate most everything else is working, such as the wifi card so we can access it remotely via ssh and a USB optical mouse lights up when connected so USB is also working. Obviously, the disk is also working. The Chromebook is configured to boot from the device's SD card slot by turning on Chrome OS developer mode options to enable booting from the SD card slot.
The mystery is that when booting the exact same 6.1.59 kernel on the bare metal instead of booting it as dom0 on Xen, it boots up with full access to the screen and we can interact with the system using the X.org windows system. But booting as dom0 with Xen, the screen is totally dark and the only access we have to the system is through the network via ssh. Also, when booting the 5.4.257 kernel with KVM in hypervisor mode, the screen works and we can interact with the system through the X.org windows system.
We also have not yet done a thorough analysis of the differences in the kernel boot logs when booting on the bare metal vs. booting as dom0 on Xen, but nothing stood out in the logs as an obvious cause of this problem after a quick look at the logs.
Any ideas why booting the same Linux kernel that results in a working X.org display on the bare metal instead as dom0 on Xen would cause the display to remain dark, but most other basic functions would work, such as network, disk, and USB?
We are trying to boot Xen on a Samsung XE303C12 Chromebook aka "snow" following the suggestions in the slide show presentiation here:
https://www.slideshare.net/xen_com_mgr/xpds16-porting-xen-on-arm-to-a-new-soc-julien-grall-arm
This device uses an exynos5250 SOC dual core 1.7 GHz with 2 MB RAM, it is a Samsung armv7 chip with virtualization extensions.
In particular, we have it working fairly well both on the bare metal with a recent 6.1.59 Linux LTS kernel and also with a recent 5.4.257 LTS kernel with KVM, the older LTS kernel version is used to test KVM because support for KVM on arm v7 was removed from Linux around kernel version 5.7. So we know we have the hypervisor mode enabled because we were able to use it with KVM.
For Xen, we are using the latest Debian build of Xen 4.17 for the Debian armhf architecture:
(XEN) Xen version 4.17.2-pre (Debian 4.17.1+2-gb773c48e36-1) (pkg-xen-devel@lists.alioth.debian.org) (arm-linux-gnueabihf-gcc (Debian 12.2.0-14) 12.2.0) debug=n Thu May 18 19:26:30 UTC 2023
The Linux kernel is a custom build that adds the Xen config kernel options (CONFIG_XEN_DOM0, etc) on top of a kernel that works well on the same Chromebook model on the bare metal. I can provide the config options of the kernel that was used if that is helpful.
Out method of booting is to have u-boot boot the Xen hypervisor and load the device tree after adding the dom0 to the otherwise unaltered device tree from the Linux kernel using u-boot fdt commands to add a /chosen node, as described on the Xen wiki and in the pages linked from there. We have also tried adding and loading an initrd.img using the device tree /chosen node but that made no difference in our tests.
We actually have the Linux LTS kernel version 6.1.59 working as dom0 with Xen using the same version of u-boot that we used for KVM, but with a big problem.
The problem we see is that when booting the 6.1.59 kernel version as dom0 with Xen, the screen is totally dark and the only way to access the system is remotely through ssh. Logs indicate most everything else is working, such as the wifi card so we can access it remotely via ssh and a USB optical mouse lights up when connected so USB is also working. Obviously, the disk is also working. The Chromebook is configured to boot from the device's SD card slot by turning on Chrome OS developer mode options to enable booting from the SD card slot.
The mystery is that when booting the exact same 6.1.59 kernel on the bare metal instead of booting it as dom0 on Xen, it boots up with full access to the screen and we can interact with the system using the X.org windows system. But booting as dom0 with Xen, the screen is totally dark and the only access we have to the system is through the network via ssh. Also, when booting the 5.4.257 kernel with KVM in hypervisor mode, the screen works and we can interact with the system through the X.org windows system.
We also have not yet done a thorough analysis of the differences in the kernel boot logs when booting on the bare metal vs. booting as dom0 on Xen, but nothing stood out in the logs as an obvious cause of this problem after a quick look at the logs.
Any ideas why booting the same Linux kernel that results in a working X.org display on the bare metal instead as dom0 on Xen would cause the display to remain dark, but most other basic functions would work, such as network, disk, and USB?