linux-kernel - Re: [PATCH 1/3] Fix COW D-cache aliasing on fork

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Message-ID: <20061020212805.GG8894@flint.arm.linux.org.uk>
Date:	Fri, 20 Oct 2006 22:28:05 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	David Miller <davem@...emloft.net>, nickpiggin@...oo.com.au,
	ralf@...ux-mips.org, Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	anemo@....ocn.ne.jp, linux-arch@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork

On Fri, Oct 20, 2006 at 02:12:11PM -0700, Linus Torvalds wrote:
> On Fri, 20 Oct 2006, Russell King wrote:
> > Well, looking at do_wp_page() I'm now quite concerned about ARM and COW.
> > I can't see how this code could _possibly_ work with a virtually indexed
> > cache as it stands.  Yet, the kernel does appear to work.
> 
> It really shouldn't need any extra code, exactly because by the time it 
> hits any page-fault, the caches had better be in sync with the physical 
> page contents _anyway_ (yes, being virtual, the caches will _duplicate_ 
> the contents, but since the pages are read-only, that aliasing should be 
> perfectly fine).

Oh, of course!  That explains why it actually works as expected!  Thanks
for filling back in that bit of swapped-out-years-ago-and-lost information.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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