Re: [Xen-devel] [PATCH v12 5/9] memory: add check_get_page_from_gfn() as a wrapper...

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Julien Grall [mailto:julien.grall@xxxxxxx]
> Sent: 01 October 2018 11:26
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; George Dunlap
> <George.Dunlap@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; Konrad
> Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Tim (Xen.org) <tim@xxxxxxx>; Wei Liu
> <wei.liu2@xxxxxxxxxx>
> Subject: Re: [PATCH v12 5/9] memory: add check_get_page_from_gfn() as a
> wrapper...
> 
> Hi Paul,
> 
> On 09/27/2018 03:33 PM, Paul Durrant wrote:
> > ...for some uses of get_page_from_gfn().
> >
> > There are many occurrences of the following pattern in the code:
> >
> >      q = <readonly look-up> ? P2M_ALLOC : P2M_UNSHARE;
> >      page = get_page_from_gfn(d, gfn, &p2mt, q);
> >
> >      if ( p2m_is_paging(p2mt) )
> >      {
> >          if ( page )
> >              put_page(page);
> >
> >          p2m_mem_paging_populate(d, gfn);
> >          return <-EAGAIN or equivalent>;
> >      }
> >
> >      if ( (q & P2M_UNSHARE) && p2m_is_shared(p2mt) )
> >      {
> >          if ( page )
> >              put_page(page);
> >
> >          return <-EAGAIN or equivalent>;
> >      }
> >
> >      if ( !page )
> >          return <-EINVAL or equivalent>;
> >
> > There are some small differences between the exact way the occurrences
> > are coded but the desired semantic is the same.
> >
> > This patch introduces a new common implementation of this code in
> > check_get_page_from_gfn() and then converts the various open-coded
> patterns
> > into calls to this new function.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > Reviewed-by: Roger Pau Monne <roger.pau@xxxxxxxxxx>
> > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > Cc: Julien Grall <julien.grall@xxxxxxx>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > Cc: Tim Deegan <tim@xxxxxxx>
> > Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> >
> > v11:
> >   - Forward declare p2m_type_t in p2m-common.h to allow the duplicate
> >     declarations of check_get_page_from_gfn() to be removed, and hence
> add
> >     Jan's R-b.
> 
> I think this would be worth adding a word in the commit message about
> the forward declaration.

Ok. I'll add something to v12.

> 
> For the Arm bits:
> 
> Acked-by: Julien Grall <julien.grall@xxxxxxx>
> 

Thanks,

  Paul

> Cheers,
> 
> --
> Julien Grall
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