From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 0/4] KVM: srcu-less dirty logging
Date: Thu, 23 Feb 2012 14:25:24 +0100
Message-ID: <1330003524.11248.11.camel@twins>
References: <20120223203300.241510a6.yoshikawa.takuya@oss.ntt.co.jp>
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	linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com
To: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
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On Thu, 2012-02-23 at 20:33 +0900, Takuya Yoshikawa wrote:
> - Stop allocating extra dirty bitmap buffer area
> 
>   According to Peter, mmu_notifier has become preemptible.  If we can
>   change mmu_lock from spin_lock to mutex_lock, as Avi said before, this
>   would be staightforward because we can use __put_user() right after
>   xchg() with the mmu_lock held 

So the 'only' thing to consider is running the end result with lockdep
enabled since the mmu locks are rather deep in the nesting tree its very
easy to accidentally cause inversions.