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Re: [Xen-devel] Tracking guest pages modified by qemu-dm / backend

To: AP <apxeng@xxxxxxxxx>
Subject: Re: [Xen-devel] Tracking guest pages modified by qemu-dm / backend
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Wed, 22 Jun 2011 09:49:53 +0100
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At 15:43 -0700 on 21 Jun (1308671006), AP wrote:
> Consider an HVM domain with EPT. When qemu-dm, backend or any other
> device model modifies DomU memory (like on a disk read or packet
> received), how does Xen track the pages that have been modified? For
> example, when an DomU is being migrated while IO is occurring.

Backends use grant tables to map guest memory; the granted pages are
marked dirty when the backend disconnects.  Qemu-dm uses the
HVMOP_modified memory hypercall to tell Xen that it's written to
the guest's memory.


Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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