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[Xen-devel] Re: xc_translate_foreign_address() returns mfn??

  • To: "List: Xen Developers" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Jun Koi" <junkoi2004@xxxxxxxxx>
  • Date: Fri, 19 Dec 2008 23:38:02 +0900
  • Delivery-date: Fri, 19 Dec 2008 06:38:27 -0800
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On Fri, Dec 19, 2008 at 7:16 PM, Jun Koi <junkoi2004@xxxxxxxxx> wrote:
> Hi,
> I looked at the function xc_translate_foreign_address(), and see that
> it walks the page table of the guest VM. So at best, it should return
> the pfn of the guest (?)
> We can see taht the Later part of the function is like this:
> ...
>        if (pt_levels >= 3)
>            mfn = (pte & L0_PAGETABLE_MASK_PAE) >> PAGE_SHIFT;
>        else
>            mfn = (pte & L0_PAGETABLE_MASK) >> PAGE_SHIFT;
> ..
> return mfn;
> So perhaps I miss something, but the "mfn" here should be "pfn", so
> this function should return pfn, not mfn as in the comment of
> xenctrl.h.
> This makes me very confused now.

So everything indicates that xc_translate_foreign_address() actually
returns gfn, not mfn like in its comment. Could anybody confirms that
the function works well on both PV and HVM?

And I think xc_map_foreign_range() actually works with gfn, not mfn.
Does it work with both PV and HVM, too?


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