From: Alexander Graf <agraf@suse.de>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH 2.4] hw/arm/boot: Increase fdt alignment
Date: Mon, 13 Jul 2015 18:20:41 +0200 [thread overview]
Message-ID: <55A3E559.7060704@suse.de> (raw)
In-Reply-To: <CAFEAcA953XYT2a4G2XT1mDavzNQAVvF9iMjuxh56Mvrb9ZdTrQ@mail.gmail.com>
On 07/13/15 18:13, Peter Maydell wrote:
> On 13 July 2015 at 16:56, Alexander Graf <agraf@suse.de> wrote:
>> The Linux kernel on aarch64 creates a page table entry at early bootup
>> that spans the 2MB range on memory spanning the fdt start address:
>>
>> [ ALIGN_DOWN(fdt, 2MB) ... ALIGN_DOWN(fdt, 2MB) + 2MB ]
>>
>> This means that when our current 4k alignment happens to fall at the end
>> of the aligned region, Linux tries to access memory that is not mapped.
>>
>> The easy fix is to instead increase the alignment to 2MB, making Linux's
>> logic always succeed.
> This is a kernel bug and should be fixed there. The booting
> protocol document is pretty clear:
> https://www.kernel.org/doc/Documentation/arm64/booting.txt
>
> "The device tree blob (dtb) must be placed on an 8-byte boundary"
While I tend to agree, we can't fix old / released kernels. So maybe we
should just fix it in both?
Alex
next prev parent reply other threads:[~2015-07-13 16:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-13 15:56 [Qemu-devel] [PATCH 2.4] hw/arm/boot: Increase fdt alignment Alexander Graf
2015-07-13 16:13 ` Peter Maydell
2015-07-13 16:20 ` Alexander Graf [this message]
2015-07-13 16:27 ` Peter Maydell
2015-07-13 16:32 ` Alexander Graf
2015-07-13 16:39 ` Alexander Graf
2015-07-13 16:41 ` Peter Maydell
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=55A3E559.7060704@suse.de \
--to=agraf@suse.de \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.