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Re: [Xen-devel] "Iomem mapping not permitted" during windows crash dump

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] "Iomem mapping not permitted" during windows crash dump under GPLPV
From: Paul Durrant <paul.durrant@xxxxxxxxxx>
Date: Tue, 2 Feb 2010 11:02:58 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
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James Harper wrote:
Keir Fraser wrote:
On 30/01/2010 08:30, "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
wrote:
So there is definitely nothing I could tell Xen to do with a DomU
PFN
that would remove the p2m mapping?
If you balloon out a page, that would do it.

Yes, it certainly would and I've seen it many times. I'm fairly sure
that by just ignoring the failed block writes coming back from
blkback/tap and carrying on you still end up with a usable MEMORY.DMP
after reboot.


Yes, that works. I still eye the error messages with contempt though :)


If you wanted to be clean, I guess you could check the data buffer addr passed to you by Windows against a map of ballooned out pages and substitute a dummy buffer in this case... but then you have the 'interesting' problem of making the dump driver aware of that map.

  Paul

--
===============================
Paul Durrant, Software Engineer

Citrix Systems (R&D) Ltd.
First Floor, Building 101
Cambridge Science Park
Milton Road
Cambridge CB4 0FY
United Kingdom
===============================

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