Hi, Simon! On 03.12.21 18:23, Simon Glass wrote: > Hi Oleksandr, > > On Thu, 2 Dec 2021 at 22:41, Oleksandr Andrushchenko > <oleksandr_andrushche...@epam.com> wrote: >> Hi, Simon! >> >> On 02.12.21 19:57, Simon Glass wrote: >>> Hi Oleksandr, >>> >>> On Thu, 2 Dec 2021 at 10:40, Oleksandr Andrushchenko >>> <oleksandr_andrushche...@epam.com> wrote: >>>> Hi, Simon! >>>> >>>> Sorry for being late to the party >>>> >>>> On 02.12.21 17:59, Simon Glass wrote: >>>>> Add an empty file to prevent build errors when building with >>>>> CONFIG_OF_SEPARATE enabled. >>>>> >>>>> The build instructions in U-Boot do not provide enough detail to build a >>>>> useful devicetree, unfortunately. >>>> Xen guest doesn't use any built-in device trees as the guest's device tree >>>> is provided >>>> by the Xen hypervisor itself and is generated at the virtual machine >>>> creation time: it is >>>> populated with memory size, number of CPUs etc. based on [1]. >>>> So, even if we provide some device tree here it must not be used by U-boot >>>> at >>>> the end of the day. Thus, it might be a reasonable solution to provide an >>>> empty device >>>> tree as you do, but put a comment that it is not used. >>> OK we can go with an empty one if we have to, but where are the >>> instructions to create the DT that is used? >> You don't need to create the device tree yourself, but instead it is >> provided by Xen and generated at run-time while creating a >> virtual machine. So, it is up to Xen to provide one. >> There are cases [1] when you may want providing a so called >> partial device tree to better tune what a virtual machine gets. >> But again, it is used by Xen toolstack outside of the virtual machine >> and serves as a sort of overlay to the generated device tree. >> So, we can provide some device tree to be embedded in U-boot, >> but it will have no practical meaning and will make more harm than good >>> I'm not even sure how to run U-Boot with Xen? The in-tree instructions >>> don't help... >> This is just a virtual machine from Xen POV, so U-boot is nothing >> different here from Linux kernel or anything else. >> Thus no specific instructions are needed nor provided > I'd like to try it out. How?? Well, it can be tricky a bit. There are number of ARM64 platforms which have Xen running: Arm, Renesas, Xilinx, iMX8, Rpi4... You can probably start from QEMU, for example OP-TEE has a way to build Xen + QEMU, please see [1]. The build has Xen in it and a virtual machine [2].
You will need to tweak [3] and put U-boot instead of the Linux kernel. I never tried that build myself, but I know it is used for OP-TEE tests for Xen. Hope this helps, Oleksandr > > Regards, > Simon [1] https://github.com/OP-TEE/manifest/blob/master/qemu_v8.xml [2] https://github.com/OP-TEE/build/tree/master/qemu_v8/xen [3] https://github.com/OP-TEE/build/blob/master/qemu_v8/xen/guest.cfg#L1