Re: [PATCH v6 0/7] hw/arm/virt: Improve address assignment for high memory regions

[Gavin Shan]

Hi Peter and Marc,

On 10/24/22 11:54 AM, Gavin Shan 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 and introduces new properties for user to
> selectively disable those 3 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
> PATCH[7]   adds properties so that high memory regions can be disabled
>
> v5: https://lists.nongnu.org/archive/html/qemu-arm/2022-10/msg00280.html
> 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-gshan@redhat.com/T/
> v1: https://lists.nongnu.org/archive/html/qemu-arm/2022-08/msg00013.html

Could you help to take a look when getting a chance? I think Connie and
Eric are close to complete the reviews, but v7 is still needed to address
extra comments from them. I hope to make v7 mergeable if possible :)

Thanks,
Gavin

> Changelog
> ==========
> v6:
>    * Pick review-by from Connie/Eric                            (Connie/Eric)
>    * Make the changes obvious in PATCH[v6 5/7]                  (Eric)
>    * Move the example to commit log and describe the legacy
>      and compact layout in code's comments in PATCH[v6 6/7]     (Eric)
>    * Comment and commit message improvements                    (Connie/Eric)
>    * Add 3 properties in PATCH[v6 7/7], allowing user to disable
>      those 3 high memory regions                                (Marc)
> 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 (7):
>    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
>    hw/arm/virt: Add properties to disable high memory regions
>
>   docs/system/arm/virt.rst |  16 ++++
>   hw/arm/virt.c            | 182 ++++++++++++++++++++++++++++++++-------
>   include/hw/arm/virt.h    |   2 +
>   3 files changed, 167 insertions(+), 33 deletions(-)