Re: [Xen-devel] Sources of page dirtying for HVM domains in Xen 3.2.x

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

Hi,

At 11:34 -0700 on 03 Oct (1223033670), Mike Sun wrote:
> Meaning that they're not marked dirty at all?  My understanding was
> that qemu-dm marked them dirty and that this dirty bitmap for DMA
> writes could be accessed.  It seems like that's what the live
> migration code uses to check for dirtied pages from qemu dma
> (init_qemu_maps(), qemu_flip_buffer()).  

qemu tracks them in its own bitmap.  What I meant is there's no marking
done inside xen for those writes, so just hooking the log-dirty bitmap
there won't catch them.

> I can see a need for a
> hypercall when qemu does the dirty marking in its code.  I may just
> save myself some trouble and pre-copy those memory pages instead of
> letting them be CoW.

Yep, if you can do that from inside qemu, that should be fine.
 
Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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