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[Xen-devel] scrubbing pages on vm pause

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] scrubbing pages on vm pause
From: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 25 May 2010 16:12:53 +0200
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
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On 05/25/2010 02:59 PM, Keir Fraser wrote:
> On 25/05/2010 13:50, "Rafal Wojtczuk" <rafal@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>>> There is no guarantee that the memory will be zeroed.
>> Interesting.
>> For my education, could you explain who is responsible for clearing memory
>> of a newborn domain ? Xend ? Could you point me to the relevant code
>> fragments ?
> New domains are not guaranteed to receive zeroed memory. The only guarantee
> Xen provides is that when it frees memory for a *dead* domain, it will scrub
> the contents before reallocation (it may not write zeroes however, in a
> debug build of Xen for example!). Other memory pages the domain freeing 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-out
by xen in that case?


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