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

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> 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...?

> 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.

Cheers,
Mark



-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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