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	<1390389916-8711-3-git-send-email-wangnan0@huawei.com>
Date: Wed, 22 Jan 2014 07:56:52 -0500
Message-ID: <CANacCWz2DdLvns9htszpwWnASrYGXQt+tHMsw4aBbjoyw-DmeQ@mail.gmail.com>
Subject: Re: [PATCH 2/3] ARM: kexec: copying code to ioremapped area
From: Vaibhav Bedia <vaibhav.bedia@gmail.com>
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To: Wang Nan <wangnan0@huawei.com>
Cc: kexec@lists.infradead.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, Geng Hui <hui.geng@huawei.com>, linux-mm@kvack.org, Eric Biederman <ebiederm@xmission.com>, Russell King <rmk+kernel@arm.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>, Linux ARM Kernel List <linux-arm-kernel@lists.infradead.org>

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On Wed, Jan 22, 2014 at 6:25 AM, Wang Nan <wangnan0@huawei.com> wrote:

> ARM's kdump is actually corrupted (at least for omap4460), mainly because
> of
> cache problem: flush_icache_range can't reliably ensure the copied data
> correctly goes into RAM. After mmu turned off and jump to the trampoline,
> kexec
> always failed due to random undef instructions.
>
> This patch use ioremap to make sure the destnation of all memcpy() is
> uncachable memory, including copying of target kernel and trampoline.
>

AFAIK ioremap on RAM in forbidden in ARM and device memory that ioremap()
ends up creating is not meant for executable code.

Doesn't this trigger the WARN_ON() in _arm_ioremap_pfn_caller)?

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<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Wed, Jan 22, 2014 at 6:25 AM, Wang Nan <span dir="ltr">&lt;<a href="mailto:wangnan0@huawei.com" target="_blank">wangnan0@huawei.com</a>&gt;</span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">ARM&#39;s kdump is actually corrupted (at least for omap4460), mainly because of<br>
cache problem: flush_icache_range can&#39;t reliably ensure the copied data<br>
correctly goes into RAM. After mmu turned off and jump to the trampoline, kexec<br>
always failed due to random undef instructions.<br>
<br>
This patch use ioremap to make sure the destnation of all memcpy() is<br>
uncachable memory, including copying of target kernel and trampoline.<br></blockquote><div><br></div><div>AFAIK ioremap on RAM in forbidden in ARM and device memory that ioremap()</div><div>ends up creating is not meant for executable code.</div>
<div><br></div><div>Doesn&#39;t this trigger the WARN_ON() in _arm_ioremap_pfn_caller)?</div></div></div></div>

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