Re: Checking guest memory pages changes from host userspace

[Alexander Graf <agraf@suse.de>]

On 21.06.2009, at 17:51, Avi Kivity <avi@redhat.com> wrote:

> On 06/19/2009 09:09 PM, Passera, Pablo R wrote:
>> Hi list,
>>         I need to monitor some guest memory pages. I need to know  
>> if the information in these pages was changed. For this, I was  
>> thinking to mark the guest memory pages in some way (like write  
>> protecting them) so a page fault is generated. Then manage this  
>> fault inside qemu. Is there some API in libkvm that allows me to do  
>> this?
>>
>
> You can use the dirty memory logging API.  vga uses this to track  
> which regions of the screen have changed, and live migration uses it  
> to allow the guest to proceed while copying its memory to the other  
> node.  It works exactly by write protecting guest memory and  
> trapping the resultant fault.

I stumbled across this on my ppc implementation: Is there an obvious  
reason we don't use the pte's dirty bit?

I don't know which operation is more frequent - writing into dirty  
mapped memory or reading the dirty map. And I have no idea how long it  
would take to find out dirty pages...

Alex


>
> -- 
> error compiling committee.c: too many arguments to function
>
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