[PATCH v4 0/6] hw/arm/virt: Improve address assignment for high memory regions

[Gavin Shan <gshan@redhat.com>]

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[1-4] preparatory work for the improvment
PATCH[5]   improve high memory region address assignment
PATCH[6]   adds 'compact-highmem' to enable or disable the optimization

History
=======
v3: https://lists.nongnu.org/archive/html/qemu-arm/2022-09/msg00258.html
v2: https://lore.kernel.org/all/20220815062958.100366-1-gshan@redhat.com/T/
v1: https://lists.nongnu.org/archive/html/qemu-arm/2022-08/msg00013.html

Changelog
==========
v4:
  * Add virt_get_high_memmap_enabled() helper                  (Eric)
  * Move 'vms->highmem_compact' and related logic from
    PATCH[v4 6/6] to PATCH[v4 5/6] to avoid git-bisect
    breakage                                                   (Eric)
  * Document the legacy and optimized high memory region
    layout in commit log and source code                       (Eric)
v3:
  * Reorder the patches                                        (Gavin)
  * Add 'highmem-compact' property for backwards compatibility (Eric)
v2:
  * Split the patches for easier review                        (Gavin)
  * Improved changelog                                         (Marc)
  * Use 'bool fits' in virt_set_high_memmap()                  (Eric)

Gavin Shan (6):
  hw/arm/virt: Introduce virt_set_high_memmap() helper
  hw/arm/virt: Rename variable size to region_size in
    virt_set_high_memmap()
  hw/arm/virt: Introduce variable region_base in virt_set_high_memmap()
  hw/arm/virt: Introduce virt_get_high_memmap_enabled() helper
  hw/arm/virt: Improve high memory region address
  hw/arm/virt: Add 'compact-highmem' property

 docs/system/arm/virt.rst |   4 ++
 hw/arm/virt.c            | 131 +++++++++++++++++++++++++++++----------
 include/hw/arm/virt.h    |   2 +
 3 files changed, 104 insertions(+), 33 deletions(-)

-- 
2.23.0