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
Thank you, Oleksandr > > Regards, > Simon [1] https://xenbits.xen.org/docs/unstable/misc/arm/passthrough.txt
