linux-kernel - Re: mmu_notifier: invalidate_range for move_page

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Message-ID: <Pine.LNX.4.64.0801311840100.26594@schroedinger.engr.sgi.com>
Date:	Thu, 31 Jan 2008 18:41:57 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Robin Holt <holt@....com>
cc:	Andrea Arcangeli <andrea@...ranet.com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: mmu_notifier: invalidate_range for move_page_tables

On Thu, 31 Jan 2008, Robin Holt wrote:

> On Thu, Jan 31, 2008 at 05:57:25PM -0800, Christoph Lameter wrote:
> > Move page tables also needs to invalidate the external references
> > and hold new references off while moving page table entries.
> 
> I must admit to not having spent any time thinking about this, but aren't
> we moving the entries from one set of page tables to the other, leaving
> the pte_t entries unchanged.  I guess I should go look, but could you
> provide a quick pointer in the proper direction as to why we need to
> recall externals when the before and after look of these page tables
> will have the same information for the TLBs.

remap changes the address of pages in a process. The pages appear at 
another address. Thus the external pte will have the wrong information if 
not invalidated.

Do a

man mremap


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