linux-kernel - Re: [PATCH 0/4] arm64: Make kexec_file

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Date:   Thu, 27 May 2021 18:39:15 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Bhupesh SHARMA <bhupesh.sharma@...aro.org>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Dave Young <dyoung@...hat.com>,
        Moritz Fischer <mdf@...nel.org>, kernel-team@...roid.com
Subject: Re: [PATCH 0/4] arm64: Make kexec_file_load honor iomem reservations

On Wed, May 26, 2021 at 08:05:27PM +0100, Marc Zyngier wrote:
> This series is a complete departure from the approach I initially sent
> almost a month ago[1]. 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.
> 
> Obviously, this is now at least 5.14 material. Given how broken
> kexec_file_load is for non-crash kernels on arm64 at the moment,
> should we at least disable it in 5.13 and all previous stable kernels?

I think it makes sense to disable it in the current and earlier kernels.

For this series:

Acked-by: Catalin Marinas <catalin.marinas@....com>