From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joanna Rutkowska <joanna@invisiblethingslab.com>
Subject: Re: scrubbing pages on vm pause
Date: Tue, 25 May 2010 16:19:48 +0200
Message-ID: <4BFBDC84.2090500@invisiblethingslab.com>
References: <C821999F.15423%keir.fraser@eu.citrix.com>
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To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Rafal Wojtczuk <rafal@invisiblethingslab.com>
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On 05/25/2010 04:13 PM, Keir Fraser wrote:
> On 25/05/2010 15:12, "Joanna Rutkowska" <joanna@invisiblethingslab.com>=

> wrote:
>=20
>>> New domains are not guaranteed to receive zeroed memory. The only gua=
rantee
>>> Xen provides is that when it frees memory for a *dead* domain, it wil=
l scrub
>>> the contents before reallocation (it may not write zeroes however, in=
 a
>>> debug build of Xen for example!). Other memory pages the domain freei=
ng the
>>> pages must scrub them itself before freeing them back to Xen.
>>>
>>
>> And what happens when we pause and save a domain? Are the pages zero-o=
ut
>> by xen in that case?
>=20
> If the original domain is subsequently destroyed then yes, Xen zeroes t=
he
> pages.
>=20

Let's consider this scenario:

xm save domain1

xm create domain2

Can the domain2 get *unscrubbed* pages that were previously used by
domain1, but were not scrubbed properly by domain1?

j.


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