From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Vrabel <david.vrabel@citrix.com>
Subject: Re: Migration memory corruption - PV backends need to
	quiesce
Date: Tue, 1 Jul 2014 11:29:21 +0100
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To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>, Tim Deegan <tim@xen.org>, Xen-devel List <xen-devel@lists.xen.org>, Paul Durrant <Paul.Durrant@citrix.com>, Jan Beulich <JBeulich@suse.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>
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On 30/06/14 10:53, Ian Campbell wrote:
> On Mon, 2014-06-30 at 10:47 +0100, David Vrabel wrote:
>
>> Using persistent grants means that backend writes may be lost since the
>> memcpy in the backend does not update the dirty bitmap and guest writes
>> to the shared ring may make the backends response writes visible.  I
>> think we may need to disable persistent grant support from blkback until
>> a mechanism for updating the dirty log is in place.
> 
> Yes, sadly I think you might be right here.

The copy in the frontend from the persistently granted pages to the
pages in the bio dirties those pages so this is actually safe.

David