There are three high memory regions, which are VIRT_HIGH_REDIST2,
VIRT_HIGH_PCIE_ECAM and VIRT_HIGH_PCIE_MMIO. Their base addresses
are floating on highest RAM address. However, they can be disabled
in several cases.
(1) One specific high memory region is disabled by developer by
toggling vms->highmem_{redists, ecam, mmio}.
(2) VIRT_HIGH_PCIE_ECAM region is disabled on machine, which is
'virt-2.12' or ealier than it.
(3) VIRT_HIGH_PCIE_ECAM region is disabled when firmware is loaded
on 32-bits system.
(4) One specific high memory region is disabled when it breaks the
PA space limit.
The current implementation of virt_set_memmap() isn't comprehensive
because the space for one specific high memory region is always
reserved from the PA space for case (1), (2) and (3). In the code,
'base' and 'vms->highest_gpa' are always increased for those three
cases. It's unnecessary since the assigned space of the disabled
high memory region won't be used afterwards.
The series intends to improve the address assignment for these
high memory regions:
PATCH[1] and PATCH[2] are cleanup and preparatory works.
PATCH[3] improves address assignment for these high memory regions
PATCH[4] moves the address assignment logic into standalone helper
History
=======
v1: https://lists.nongnu.org/archive/html/qemu-arm/2022-08/msg00013.html
Changelog
=========
v2:
* Split the patches for easier review (Gavin)
* Improved changelog (Marc)
* Use 'bool fits' in virt_set_high_memmap() (Eric)