Re: [Xen-devel] Why does xc_map_foreign_range() refuse to map pfns below 1M from a domU

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-12-04 at 10:54 +0000, Jan Beulich wrote:
> >>> On 04.12.13 at 11:45, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > Correct. The check for mapping domain 0's 1:1 map is overly broad I
> > think, and erroneously prevents a domU from mapping a foreign PFN < 1M.
> 
> But that's the source of my not understanding: xen_make_pte()
> derives addr from the passed in pte, and that pte can - for a
> foreign domain's page - hardly hold a PFN. Otherwise how would
> the translation to MFN be supposed to happen? Yet, if it's a
> machine address that's coming in, it can't point into the low 1Mb.

Isn't it a foreign gpfn at this point, which for an HVM guest is
actually a PFN not an MFN?

You are making me think I might be talking out my a**e though, because
what is a foreign mapping even doing in xen_make_pte -- those need to be
instantiated in a special way.

Ian.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel