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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Mon, 31 May 2021 21:36:34 +0200
Message-ID: <CAMj1kXFjsdnNy=7yMwCQsAyKrratU0_9eemviHug6VeGbSEmOg@mail.gmail.com>
Subject: Re: [PATCH v2 0/5] arm64: Make kexec_file_load honor iomem reservations
To:     Marc Zyngier <maz@kernel.org>
Cc:     kexec@lists.infradead.org,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        James Morse <james.morse@arm.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Hanjun Guo <guohanjun@huawei.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Bhupesh SHARMA <bhupesh.sharma@linaro.org>,
        AKASHI Takahiro <takahiro.akashi@linaro.org>,
        Dave Young <dyoung@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Moritz Fischer <mdf@kernel.org>,
        Android Kernel Team <kernel-team@android.com>
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On Mon, 31 May 2021 at 11:57, Marc Zyngier <maz@kernel.org> 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@kernel.org
> [1] https://lore.kernel.org/r/20210526190531.62751-1-maz@kernel.org
>
> 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
>