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Subject: Re: [PATCH v11 4/6] mm: function to offer a page block on the free
 list
References: <1497004901-30593-1-git-send-email-wei.w.wang@intel.com>
 <1497004901-30593-5-git-send-email-wei.w.wang@intel.com>
 <b92af473-f00e-b956-ea97-eb4626601789@intel.com>
 <20170612181354-mutt-send-email-mst@kernel.org>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <9d0900f3-9df5-ac63-4069-2d796f2a5bc7@intel.com>
Date: Mon, 12 Jun 2017 09:42:36 -0700
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Wei Wang <wei.w.wang@intel.com>, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, david@redhat.com, cornelia.huck@de.ibm.com, akpm@linux-foundation.org, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com

On 06/12/2017 09:28 AM, Michael S. Tsirkin wrote:
> 
>> The hypervisor is going to throw away the contents of these pages,
>> right?
> It should be careful and only throw away contents that was there before
> report_unused_page_block was invoked.  Hypervisor is responsible for not
> corrupting guest memory.  But that's not something an mm patch should
> worry about.

That makes sense.  I'm struggling to imagine how the hypervisor makes
use of this information, though.  Does it make the pages read-only
before this, and then it knows if there has not been a write *and* it
gets notified via this new mechanism that it can throw the page away?

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