netdev - Re: [PATCH 2/3] e1000e: Useset_memory_ro()/set_memory

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Message-ID: <20080924175358.GA2591@phobos.i.cabal.ca>
Date:	Wed, 24 Sep 2008 13:53:58 -0400
From:	Kyle McMartin <kyle@...hat.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:	jeff@...zik.org, mingo@...e.hu, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	jesse.brandeburg@...el.com, john.ronciak@...el.com,
	Bruce Allan <bruce.w.allan@...el.com>
Subject: Re: [PATCH 2/3] e1000e: Useset_memory_ro()/set_memory_rw() to
	protect flash memory

On Tue, Sep 23, 2008 at 03:45:54PM -0700, Jeff Kirsher wrote:
> +#ifdef _ASM_X86_CACHEFLUSH_H
> +	set_memory_rw((unsigned long)hw->flash_address,
> +	              hw->flash_len >> PAGE_SHIFT);
> +#endif
>  	writew(val, hw->flash_address + reg);
> +#ifdef _ASM_X86_CACHEFLUSH_H
> +	set_memory_ro((unsigned long)hw->flash_address,
> +	              hw->flash_len >> PAGE_SHIFT);
> +#endif
>  }

Hi Jeff,

You're making the entire read-only mapping read-write for the single
writel call... why not just limit it to the page that the writel is
targetting?

regards, Kyle
[sorry, I've only been following this at a glance, but it's somewhat
 important for rawhide... does someone have a way to reproduce this at
 whim? Has someone tried catching it using an IOMMU on one of the newer
 Intel boxes, if it is a DMA going awry?]
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