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Date:   Tue, 01 Jun 2021 09:36:27 +0100
Message-ID: <87y2bu0yno.wl-maz@kernel.org>
From:   Marc Zyngier <maz@kernel.org>
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>
Subject: Re: [PATCH v2 1/5] arm64: kexec_file: Forbid non-crash kernels
In-Reply-To: <CAMj1kXFNUAtXPzO+EbMzZQPxgst4BMEUuYbrWwYer3P9trYdLQ@mail.gmail.com>
References: <20210531095720.77469-1-maz@kernel.org>
        <20210531095720.77469-2-maz@kernel.org>
        <CAMj1kXFNUAtXPzO+EbMzZQPxgst4BMEUuYbrWwYer3P9trYdLQ@mail.gmail.com>
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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.