plat: Rework paged memory init

[michpappas]

Prerequisite checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Ran the checkpatch.uk on your commit series before opening this PR;
• Updated relevant documentation.

Base target

• Architecture(s): [N/A]
• Platform(s): [N/A]
• Application(s): [N/A]

Additional configuration

Description of changes

This series reworks the initialization of paged memory to provide a more flexible implementation that is capable of handling regions beyond the limits defined in the boot page-tables. The motivation for this change is to allow mapping device regions that are unknown at compile-time, such as Unprotected IPA Alias regions of Arm CCA Realms [1][2], the address of which depends on the executing platform.

This rework has side-effects on the way device MMIO regions are mapped. To address these requirements, this PR performs the following changes:

• Introduce early init boot stage in kvm/arm64.
• Add early_init to drivers that use MMIO, and have these drivers register bootinfo mrds for these regions during early_init.
• Add runtime mapping of MMIO regions to the initialization of relevant drivers.

All the above are described in further detail in the sections that follow.

Additional fixes include:

• lib/ukbus: Use the correct init class and priority.
• plat/drivers/uktty: Clean up driver init (ns16550 and pl011).
• plat/drivers/uktty: Move driver init to uk_inttab (ns16550 and pl011).
• plat/kvm/arm64: Remove console registration from platform setup.

Rework of paged memory init

Under the new scheme, bootinfo is simplified to only contain valid memory regions. Upon paged memory initialization these regions are either mapped with the protections defined in their mrd, or are already mapped, in which case only their protections are updated. An exception to this is mrds of the UKPLAT_MEMRT_DEVICE type, that are ignored to allow MMIO regions mapped during early device initialization to remain mapped.

Any memory not defined in bootinfo is unmapped. The theoretical bounds used as a reference are platform-specific and are defined in a newly introduced platform.h that must be provided by all platforms.

Early device initialization

early_init is invoked as the last call of early boot code, as soon as the stack and MMU are enabled.

Early devices are initialized before bootinfo setup, as the latter depends on UART for debug messages.

Early devices can use the APIs provided by libfdt / ACPI to obtain any information required from the firmware, such as device regions and the kernel command line.

Drivers that register with early_init are updated to append mrds of their MMIO regions to bootinfo. That is required so that their regions are not unmapped by paged memory init. The mrds added during early_init to bootinfo must use the newly introduced UKPLAT_MEMRT_DEVICE type.

Be aware that early drivers should not call ukplat_bootinfo_coalesce, as mrd coalescing is performed once at the end of bootinfo_setup, which is now performed as to the last step of early_init.

Notice that:

• early_init is currently introduced in kvm/arm64, as it is the only platform that involves early initialization of drivers that use MMIO.
• early_init is currently implemented as a simple placeholder from where drivers can add manual calls of their early_init functions. This should be replaced with an early inittab as soon as bootinfo is moved out of plat.

Late (i.e. non-early) device initialization

Given that all memory that is not backed by an mrd is unmapped during paged memory init, devices that don't register mrds during early init are now required to map their regions during probing. To address this requirement this PR updates relevant drivers to map their MMIO regions dynamically.

References

[1] Realm Management Monitor Specification DEN0137 Sect. D2.1
[2] #964

GitHub-Depends-On: #972
GitHub-Depends-On: #1212
GitHub-Depends-On: #1346