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Re: [Xen-devel] What's allocated on head 1M region of domU?

Mark Williamson wrote:
>> I'm now try to read and write puseud physical memory of domU from Dom0
>> with xenaccess(this is using libxc).
>> #http://xenaccess.sourceforge.net/
> Ah, cool.  I'd not heard much about XenAccess for a while, but I see they're 
> still progressing nicely - cool.

>> With xenaccess, I'm succeeded read and writing almost of the memory. But
>> It fail when I try to access head 1M region and some bit regions.
>> To be precise, xc_map_foreign_range() of libxc returns error code.
>> ** <javascript:goWordLink("to")>
> What error code do you get?  Are you trying to map the first meg all at once 
> and it's failing, or does it fail if you map any page in the first meg?  What 
> exactly is the call that's failing?
> I guess if you were trying to map the guest's shared_info page then you might 
> be disallowed...?
I try to map no all at once.
I've figured out that top xen kernel is sitting on top 1M region :-|

thanks Mark.

>> What's allocated on head 1M region of domU?
>> #and , Can I get a document about memory allocation of dom0 and DomU
>> somewhere?
> See the comments starting around line 476 of xen/include/public/xen.h, which 
> describes the start of day memory layout and defines some of the structures 
> involved.  This will not be the same once the guest is up and running because 
> the guest will allocate its own full pagetables and make its own decisions 
> about where it wants to put stuff.  However, it'll at least give you some 
> clues about how the guest is built initially...  I hope this helps you some.
I read the parts you suggested to me.
It helps me great :-)


HPCS lab
4th grade student of Colledge of Information Science, University of Tsukuba

Ryo Kanbayashi

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