Re: [Xen-devel] [hybrid]: code review for function mapping pfn to foreign mfn

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Thu, 26 Apr 2012 10:08:47 +0100
Tim Deegan <tim@xxxxxxx> wrote:

> At 16:06 -0700 on 24 Apr (1335283603), Mukesh Rathor wrote:
> > On Tue, 24 Apr 2012 10:36:26 +0100
> > Tim Deegan <tim@xxxxxxx> wrote:
> > 
> > > At 18:37 -0700 on 23 Apr (1335206229), Mukesh Rathor wrote:
> > > > On Thu, 19 Apr 2012 15:15:27 +0100
> > > > Tim Deegan <tim@xxxxxxx> wrote:
> > 
> > >you still have this mapping.  You should take a PGT_writeable_page
> > >typecount, too, if the foreign domain isn't in paging_mode_external
> > 
> > Ok, I've it as:
> >     if (paging_mode_external(fdom)) {
> >         if (get_page_from_pagenr(mfn, fdom) == 0)
> >         failed = 1;
> >     } else {
> >         if (get_page_and_type_from_pagenr(mfn, PGT_writable_page,
> > fdom,0,0)) failed = 1;
> >     }
> > 
> > But then later fails when it tries to pin the page,
> > MMUEXT_PIN_L4_TABLE, from the lib at:
> 
> What's trying to pin an l4 table?  I thought your hybrid dom0 didn't
> use the PV MMU.
> 
> Tim.

Right, hybrid doesn't use PV mmu. 
Here, xl/xc is building a pv guest while running on *hybrid* dom0. 
As a result, privcmd is calling this function to map
foreign mfns to pfns: 

xc_dom_x86.c:
      arch_setup_bootlate -> pin_table -> xc_mmuext_op().

thanks,
Mukesh

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