Xen support

[natto1784]

Aim

This PR aims to showcase how Xen support can be added to baremetal and FreeRTOS binaries

Changes

Xen

• Parts taken from mini-os source tree and modified to work with this tree
• Basic hypercall infrastructure
• Basic output support for both Xen and Xen PV console
• Partial event channel and HVM support, done mainly to support the above.

Build system

• --enable-xen flag to enable Xen support in project.js
• ENABLE_XEN variable for makefile support
• Conditional XEN_ENABLED define in C and assembly files
• Conditional compilation of the Xen part of code under /drivers/xen
• Conditional address changes in the linker template for am62 a53 examples

dpl (both freertos and nortos)

• Added the linux kernel zImage header to the binary for it to be able to be recognized by Xen
• Print to Xen/PV console by default if Xen is enabled

Notes

• Code style for the Xen code is still the same as mini-os source code, except a few public functions
• No TI license headers are present in the new files yet
• am62p does not have a53 support yet, but it can be enabled easily by following how it was enabled for am62
• No peripherals have been tested yet, but passthroughing a UART and using that instead of the Xen/PV console should work just fine.

Potential TODOs

• Changes to example templates
• Add some basic examples for Xen
• Conditionally add Xen to an existing component instead of a standalone component. This would allow us to build binaries without linking this new library.

[natto1784]

TODO: Passing the iomem region for timer6 in xen and mapping interrupt 158 works and ClockP_init() works fine after this too, however, HwiP_enable() fails, see why msr daifclr #2 fails. For now disable ClockP_init() for Xen.