Date: Thu, 31 Jan 2008 18:41:57 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Robin Holt <holt@sgi.com>
cc: Andrea Arcangeli <andrea@qumranet.com>, Avi Kivity <avi@qumranet.com>,
       Izik Eidus <izike@qumranet.com>, kvm-devel@lists.sourceforge.net,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, steiner@sgi.com,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       daniel.blueman@quadrics.com
Subject: Re: mmu_notifier: invalidate_range for move_page_tables
In-Reply-To: <20080201023815.GC26420@sgi.com>
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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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