linux-kernel - Re: [PATCH] arm: Prevent memory aliasing on non-LPAE kernels

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Date:	Fri, 31 May 2013 00:24:13 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Stepan Moskovchenko <stepanm@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	David Brown <davidb@...eaurora.org>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Daniel Walker <dwalker@...o99.com>
Subject: Re: [PATCH] arm: Prevent memory aliasing on non-LPAE kernels

On Thursday 30 May 2013 14:45:20 Stepan Moskovchenko wrote:
> 
>  void __init early_init_dt_add_memory_arch(u64 base, u64 size)
>  {
> +#ifndef CONFIG_ARM_LPAE
> +       if (base > ((phys_addr_t)~0)) {
> +               pr_crit("Ignoring memory at 0x%08llx due to lack of LPAE support\n",
> +                       base);
> +               return;
> +       }
> +
> +       if (size > ((phys_addr_t)~0))
> +               size = ((phys_addr_t)~0);
> +
> +       /* arm_add_memory() already checks for the case of base + size > 4GB */
> +#endif
>         arm_add_memory(base, size);
>  }

This looks wrong for the case where 'base' is between >0 and 4GB and 'size'
makes it spill over the 4GB boundary. You need to set
'size = (phys_addr_t)~0 - base' then.

	Arnd
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