linux-kernel - Re: [PATCH v2 4/6] arm/dt: probe for platforms via the device tree

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Message-ID: <alpine.LFD.2.00.1101311709280.8580@xanadu.home>
Date:	Mon, 31 Jan 2011 17:27:20 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Grant Likely <grant.likely@...retlab.ca>
cc:	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	devicetree-discuss@...ts.ozlabs.org,
	lkml <linux-kernel@...r.kernel.org>,
	Lennert Buytenhek <buytenh@...tstofly.org>,
	Olof Johansson <olof@...om.net>, john.linn@...inx.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 4/6] arm/dt: probe for platforms via the device tree

On Mon, 31 Jan 2011, Grant Likely wrote:

> If a dtb is passed to the kernel then the kernel needs to iterate
> through compiled-in mdescs looking for one that matches and move the
> dtb data to a safe location before it gets accidentally overwritten by
> the kernel.
> 
> This patch creates a new function, setup_machine_fdt() which is
> analogous to the setup_machine_atags() created in the previous patch.
> It does all the early setup needed to use a device tree machine
> description.  It also creates arm_unflatten_device_tree() which copies
> the dtb into an allocated buffer and unflattens it into the live-tree
> representation.
> 
> v2: Changed to save the dtb by copying into an allocated buffer.
>     - Since the dtb will very likely be passed in the first 16k of ram
>       where the interrupt vectors live, memblock_reserve() is
>       insufficient to protect the dtb data.

This is wrong.  The vector page can be allocated anywhere.  It is 
currently allocated with memblock_alloc(), so if you memblock_reserve() 
the dtb soon enough then it should be safe and the vector page or 
whatever will be allocated somewhere else.

What was the actual problem?


Nicolas
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