Date: Thu, 31 Jan 2008 18:26:36 -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: [PATCH] mmu notifiers #v5
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On Thu, 31 Jan 2008, Robin Holt wrote:

> > Mutex locking? Could you be more specific?
> 
> I think he is talking about the external locking that xpmem will need
> to do to ensure we are not able to refault pages inside of regions that
> are undergoing recall/page table clearing.  At least that has been my
> understanding to this point.

Right this has to be something like rw spinlock. Its needed for both 
GRU/XPmem. Not sure about KVM.

Take the read lock for invalidate operations. These can occur 
concurrently. (Or a simpler implementation for the GRU may just use a 
spinlock).

The write lock must be held for populate operations.

Lock can be refined as needed by the notifier driver. F.e. locking could 
be restricted to certain ranges.

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