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Re: [PATCH] of: Specify initrd location using 64-bit

To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH] of: Specify initrd location using 64-bit
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Mon, 1 Jul 2013 09:59:33 +0200
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>, Nicolas Pitre <nicolas.pitre@linaro.org>, linux-mips <linux-mips@linux-mips.org>, Aurelien Jacquiot <a-jacquiot@ti.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Max Filippov <jcmvbkbc@gmail.com>, Paul Mackerras <paulus@samba.org>, Jonas Bonn <jonas@southpole.se>, Russell King <linux@arm.linux.org.uk>, linux-c6x-dev@linux-c6x.org, "the arch/x86 maintainers" <x86@kernel.org>, "arm@kernel.org" <arm@kernel.org>, Rob Herring <robherring2@gmail.com>, Grant Likely <grant.likely@linaro.org>, Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>, linux-xtensa@linux-xtensa.org, James Hogan <james.hogan@imgtec.com>, devicetree-discuss <devicetree-discuss@lists.ozlabs.org>, Rob Herring <rob.herring@calxeda.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Chris Zankel <chris@zankel.net>, Vineet Gupta <vgupta@synopsys.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Ralf Baechle <ralf@linux-mips.org>, "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
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References: <1371775956-16453-1-git-send-email-santosh.shilimkar@ti.com> <51C4171C.9050908@linutronix.de> <51C48B5A.2040404@ti.com> <51CCA67C.2010803@gmail.com> <CACxGe6vOH0sCFVVXrYqD3dbYdOvithVu7-d1cvy5885i8x_Myw@mail.gmail.com> <20130628134931.GD21034@game.jcrosoft.org> <51CE1F92.3070802@ti.com> <51D1345B.8020509@linutronix.de>
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On Mon, Jul 1, 2013 at 9:48 AM, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
> On 06/29/2013 01:43 AM, Santosh Shilimkar wrote:
>> Apart from waste of 32bit, what is the other concern you
>> have ?
>
> You pass a u64 as a physical address which is represented in other
> parts of the kernel (for a good reason) by phys_addr_t.
>
>> I really want to converge on this patch because it
>> has been a open ended discussion for quite some time. Does
>> that really break any thing on x86 or your concern is more
>> from semantics of the physical address.
> You want to have your code in so you can continue with your work, that
> is okay. The other two arguments why u64 here is a good thing was "due
> to what I said earlier" and "+1" and I don't have the time to look
> that up.
>
> There should be no problems on x86 if this goes in as it is now.
>
> But think about this: What happens if you boot your ARM device without
> PAE and your initrd is in the upper region? If you are lucky the kernel
> looks at a different place where it also has a read permission, notices
> nothing sane is there, writes a message and continues. And if it is not
> allowed to read? It is clearly the user's fault for booting a non-PAE
> kernel.

That's actual the original reason: DT has it as 64 bit, and passes it to a
32 bit kernel when running in 32 bit mode without PAE.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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