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
v4: https://lists.nongnu.org/archive/html/qemu-arm/2022-10/msg00067.html
v3: https://lists.nongnu.org/archive/html/qemu-arm/2022-09/msg00258.html
v2: https://lore.kernel.org/all/20220815062958.100366-1-gs...@redhat.com/T/
v1: https://lists.nongnu.org/archive/html/qemu-arm/2022-08/msg00013.html
Changelog
==========
v5:
* Pick review-by and tested-by (Connie/Zhenyu)
* Add extra check in PATCH[v5 4/6] (Connie)
* Improve comments about compatibility for disabled regions
in PATCH[v5 5/6] (Connie)
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 assignment
hw/arm/virt: Add 'compact-highmem' property
docs/system/arm/virt.rst | 4 ++
hw/arm/virt.c | 135 +++++++++++++++++++++++++++++----------
include/hw/arm/virt.h | 2 +
3 files changed, 108 insertions(+), 33 deletions(-)
--
2.23.0
