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Date: Tue, 01 Jun 2021 09:36:27 +0100
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From: Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH v2 1/5] arm64: kexec_file: Forbid non-crash kernels
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To: Ard Biesheuvel <ardb@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>, "# 3.4.x" <stable@vger.kernel.org>

On Mon, 31 May 2021 20:37:49 +0100,
Ard Biesheuvel <ardb@kernel.org> wrote:
> 
> On Mon, 31 May 2021 at 11:57, Marc Zyngier <maz@kernel.org> wrote:
> >
> > It has been reported that kexec_file doesn't really work on arm64.
> > It completely ignores any of the existing reservations, which results
> > in the secondary kernel being loaded where the GICv3 LPI tables live,
> > or even corrupting the ACPI tables.
> >
> > Since only crash kernels are imune to this as they use a reserved
> > memory region, disable the non-crash kernel use case. Further
> > patches will try and restore the functionality.
> >
> > Reported-by: Moritz Fischer <mdf@kernel.org>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Cc: stable@vger.kernel.org # 5.10
> 
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> 
> ... but do we really only need this in 5.10 and not earlier?

We *do* need something in earlier kernel (as mentioned in the cover
letter), but not this patch (arch_kexec_locate_mem_hole doesn't exist
there, so there is nothing to override).

I guess that completely disabling CONFIG_KEXEC_FILE on arm64 is the
way to go for 5.4 and earlier, as I don't think there is any crash
kernel support there.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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