Re: [Xen-devel] [PATCH 7/8] x86/mm: handle foreign mappings in p2m_entry_modify

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Feb 06, 2019 at 09:59:30AM -0700, Jan Beulich wrote:
> >>> On 30.01.19 at 11:36, <roger.pau@xxxxxxxxxx> wrote:
> > --- a/xen/include/asm-x86/p2m.h
> > +++ b/xen/include/asm-x86/p2m.h
> > @@ -933,9 +933,12 @@ struct hvm_ioreq_server *p2m_get_ioreq_server(struct 
> > domain *d,
> >                                                unsigned int *flags);
> >  
> >  static inline void p2m_entry_modify(struct p2m_domain *p2m, p2m_type_t nt,
> > -                                    p2m_type_t ot, unsigned int level)
> > +                                    p2m_type_t ot, mfn_t nfn, mfn_t ofn,
> > +                                    unsigned int level)
> >  {
> > -    if ( level != 1 || nt == ot )
> > +    struct page_info *pg;
> > +
> > +    if ( level != 1 || (nt == ot && mfn_eq(nfn, ofn)) )
> >          return;
> >  
> >      switch ( nt )
> > @@ -948,6 +951,17 @@ static inline void p2m_entry_modify(struct p2m_domain 
> > *p2m, p2m_type_t nt,
> >          p2m->ioreq.entry_count++;
> >          break;
> >  
> > +    case p2m_map_foreign:
> > +        pg = mfn_to_page(nfn);
> > +
> > +        if ( !pg || !page_get_owner_and_reference(pg) )
> 
> mfn_to_page() can't return NULL, can it? You may want to ASSERT()
> beforehand that the MFN is not INVALID_MFN, though.

I've added ASSERT(mfn_valid(mfn)) and the same below. I think it's
safer to use mfn_valid rather that only checking against INVALID_MFM.

Thanks, Roger.

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