[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Tracking guest pages modified by qemu-dm / backend
On Fri, Jun 24, 2011 at 1:40 AM, Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote: > At 11:06 -0700 on 23 Jun (1308827188), AP wrote: >> On Wed, Jun 22, 2011 at 1:49 AM, Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote: >> > Hi, >> > >> > 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. >> >> From what I see for EPT/HAP, log dirty is turned on only during domain >> save. > > It's also used to track just the virtual framebuffer so qemu can avoid > having to compute which parts of the screen to send over VNC. > > But for general memory it's only used during save, because there's no > need for it otherwise. If you're confused about that maybe you should > read the original paper on Xen live migration: > http://www.cl.cam.ac.uk/research/srg/netos/papers/2005-nsdi-migration.pdf Sorry I think I did not phrase my question well. What I was not able to understand was how / where the granted pages were being marked dirty w.r.t EPT after the backend disconnects. Thanks, AP _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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