linux-kernel - Re: [PATCH] mmu notifiers #v5

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Message-ID: <Pine.LNX.4.64.0801311824360.25839@schroedinger.engr.sgi.com>
Date:	Thu, 31 Jan 2008 18:26:36 -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: [PATCH] mmu notifiers #v5

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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