Re: [PATCH v3 0/5] hw/arm/virt: Improve address assignment for high memory regions

[Zhenyu Zhang]

[PATCH v3 0/5] hw/arm/virt: Improve address assignment for high memory regions
Author: Gavin Shan <gshan@redhat.com>
Date:   Thu Sep 22 07:13:45 2022 +0800

    PATCH[1-3] preparatory work for the improvment
    PATCH[4]   improve high memory region address assignment
    PATCH[5]   adds 'highmem-compact' to enable or disable the optimization

    Signed-off-by: Gavin Shan <gshan@redhat.com>

The patchs works well on "IPA Size Limit: 40" FUJITSU machine.
I added some debug code to show high memory region address.
The test results are as expected.

1. virt-7.2 default
# /home/qemu/build/qemu-system-aarch64 -accel kvm -cpu host -machine
virt-7.2 -m 4G,maxmem=511G -monitor stdio
=====> virt_set_high_memmap: pa_bits=40, base=0x8000000000
[HIGH_GIC_REDIST2]: disabled, highest_gpa=0x7fffffffff    [no] [yes]
[HIGH_PCIE_ECAM]: disabled, highest_gpa=0x7fffffffff    [no] [yes]
[HIGH_PCIE_MMIO] enabled, highest_gpa=0xffffffffff

2. When virt-7.2,highmem-compact=off
# /home/qemu/build/qemu-system-aarch64 -accel kvm -cpu host -machine
virt-7.2,highmem-compact=off -m 4G,maxmem=511G -monitor stdio
=====> virt_set_high_memmap: pa_bits=40, base=0x8000000000
[HIGH_GIC_REDIST2]: disabled, highest_gpa=0x8003ffffff    [no] [yes]
[HIGH_PCIE_ECAM]: disabled, highest_gpa=0x801fffffff    [no] [yes]
[HIGH_PCIE_MMIO]: disabled, highest_gpa=0x801fffffff    [no] [no]

3. virt-7.1 default
# /home/qemu/build/qemu-system-aarch64 -accel kvm -cpu host -machine
virt-7.1 -m 4G,maxmem=511G -monitor stdio
=====> virt_set_high_memmap: pa_bits=40, base=0x8000000000
[HIGH_GIC_REDIST2]: disabled, highest_gpa=0x8003ffffff    [no] [yes]
[HIGH_PCIE_ECAM]: disabled, highest_gpa=0x801fffffff    [no] [yes]
[HIGH_PCIE_MMIO]: disabled, highest_gpa=0x801fffffff    [no] [no]

2. When virt-7.1,highmem-compact=on
# /home/qemu/build/qemu-system-aarch64 -accel kvm -cpu host -machine
virt-7.1,highmem-compact=on -m 4G,maxmem=511G -monitor stdio
=====> virt_set_high_memmap: pa_bits=40, base=0x8000000000
[HIGH_GIC_REDIST2]: disabled, highest_gpa=0x7fffffffff    [no] [yes]
[HIGH_PCIE_ECAM]: disabled, highest_gpa=0x7fffffffff    [no] [yes]
[HIGH_PCIE_MMIO] enabled, highest_gpa=0xffffffffff


Tested-by: Zhenyu Zhang<zhenyzha@redhat.com>

On Thu, Sep 22, 2022 at 7:13 AM Gavin Shan <gshan@redhat.com> wrote:
>
> 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[1-3] preparatory work for the improvment
> PATCH[4]   improve high memory region address assignment
> PATCH[5]   adds 'highmem-compact' to enable or disable the optimization
>
> History
> =======
> 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
> ==========
> 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 (5):
>   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: Improve high memory region address assignment
>   hw/arm/virt: Add 'highmem-compact' property
>
>  docs/system/arm/virt.rst |   4 ++
>  hw/arm/virt.c            | 116 ++++++++++++++++++++++++++++-----------
>  include/hw/arm/virt.h    |   2 +
>  3 files changed, 89 insertions(+), 33 deletions(-)
>
> --
> 2.23.0
>