Re: [PATCH v2 0/5] arm64: Make kexec_file_load honor iomem reservations

[Ard Biesheuvel]

On Mon, 31 May 2021 at 11:57, Marc Zyngier <maz@xxxxxxxxxx> wrote:
>
> This series is a complete departure from the approach I initially sent
> almost a month ago[0]. Instead of trying to teach EFI, ACPI and other
> subsystem to use memblock, I've decided to stick with the iomem
> resource tree and use that exclusively for arm64.
>
> This means that my current approach is (despite what I initially
> replied to both Dave and Catalin) to provide an arm64-specific
> implementation of arch_kexec_locate_mem_hole() which walks the
> resource tree and excludes ranges of RAM that have been registered for
> any odd purpose. This is exactly what the userspace implementation
> does, and I don't really see a good reason to diverge from it.
>
> Again, this allows my Synquacer board to reliably use kexec_file_load
> with as little as 256M, something that would always fail before as it
> would overwrite most of the reserved tables.
>
> Although this series still targets 5.14, the initial patch is a
> -stable candidate, and disables non-kdump uses of kexec_file_load. I
> have limited it to 5.10, as earlier kernels will require a different,
> probably more invasive approach.
>
> Catalin, Ard: although this series has changed a bit compared to v1,
> I've kept your AB/RB tags. Should anything seem odd, please let me
> know and I'll drop them.
>

Fine with me.

> Thanks,
>
>         M.
>
> * From v1 [1]:
>   - Move the overlap exclusion into find_next_iomem_res()
>   - Handle child resource not overlapping with parent
>   - Provide walk_system_ram_excluding_child_res() as a top level
>     walker
>   - Simplify arch-specific code
>   - Add initial patch disabling non-crash kernels
>
> [0] https://lore.kernel.org/r/20210429133533.1750721-1-maz@xxxxxxxxxx
> [1] https://lore.kernel.org/r/20210526190531.62751-1-maz@xxxxxxxxxx
>
> Marc Zyngier (5):
>   arm64: kexec_file: Forbid non-crash kernels
>   kexec_file: Make locate_mem_hole_callback global
>   kernel/resource: Allow find_next_iomem_res() to exclude overlapping
>     child resources
>   kernel/resource: Introduce walk_system_ram_excluding_child_res()
>   arm64: kexec_image: Restore full kexec functionnality
>
>  arch/arm64/kernel/kexec_image.c | 39 ++++++++++++++++
>  include/linux/ioport.h          |  3 ++
>  include/linux/kexec.h           |  1 +
>  kernel/kexec_file.c             |  6 +--
>  kernel/resource.c               | 82 +++++++++++++++++++++++++++++----
>  5 files changed, 119 insertions(+), 12 deletions(-)
>
> --
> 2.30.2
>