Re: [Xen-devel] [PATCH v5 02/23] x86/mm: export get_page_from_mfn

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Sep 22, 2017 at 05:44:58AM -0600, Jan Beulich wrote:
> >>> On 14.09.17 at 14:58, <wei.liu2@xxxxxxxxxx> wrote:
> > --- a/xen/arch/x86/mm.c
> > +++ b/xen/arch/x86/mm.c
> > @@ -705,22 +705,6 @@ bool map_ldt_shadow_page(unsigned int offset)
> >      return true;
> >  }
> >  
> > -
> > -static bool get_page_from_mfn(mfn_t mfn, struct domain *d)
> > -{
> > -    struct page_info *page = mfn_to_page(mfn);
> > -
> > -    if ( unlikely(!mfn_valid(mfn)) || unlikely(!get_page(page, d)) )
> > -    {
> > -        gdprintk(XENLOG_WARNING,
> > -                 "Could not get page ref for mfn %"PRI_mfn"\n", 
> > mfn_x(mfn));
> > -        return false;
> > -    }
> > -
> > -    return true;
> > -}
> > -
> > -
> >  static int get_page_and_type_from_mfn(
> >      mfn_t mfn, unsigned long type, struct domain *d,
> >      int partial, int preemptible)
> > diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
> > index bef45e8e9f..7670912e0a 100644
> > --- a/xen/include/asm-x86/mm.h
> > +++ b/xen/include/asm-x86/mm.h
> > @@ -369,6 +369,20 @@ int  get_page_from_l1e(
> >      l1_pgentry_t l1e, struct domain *l1e_owner, struct domain *pg_owner);
> >  void put_page_from_l1e(l1_pgentry_t l1e, struct domain *l1e_owner);
> >  
> > +static inline bool get_page_from_mfn(mfn_t mfn, struct domain *d)
> > +{
> > +    struct page_info *page = __mfn_to_page(mfn_x(mfn));
> 
> Why can this not remain to be mfn_to_page(mfn)? The header has
> been introduced only in the immediately preceding patch, so there
> can't be users of the header not coping with this. And once other
> code includes this header, it should be made type-safe first.

I think you misread.  This is asm-x86/mm.h, not pv/mm.h. This header
file has been used in many places. 

Furthermore, this patch introduces no change. If you look at mm.c at the
beginning:

   #undef mfn_to_page
   #define mfn_to_page(mfn) __mfn_to_page(mfn_x(mfn))

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