Re: [Xen-devel] [PATCH v1 2/8]: PVH mmu changes

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-10-03 at 23:29 +0100, Mukesh Rathor wrote:
> On Wed, 3 Oct 2012 16:42:43 +0100
> Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 
> > 
> > > diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> > > index 6a198e4..6c5ad83 100644
> > > --- a/include/xen/xen-ops.h
> > > +++ b/include/xen/xen-ops.h
> > > @@ -24,9 +24,19 @@ int xen_create_contiguous_region(unsigned long
> > > vstart, unsigned int order, void
> > > xen_destroy_contiguous_region(unsigned long vstart, unsigned int
> > > order); struct vm_area_struct;
> > > +struct xen_pvh_pfn_info;
> > 
> > If you move the struct def'n up you don't need this forward decl.
> > 
> > >  int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
> > >                          unsigned long addr,
> > >                          unsigned long mfn, int nr,
> > > -                        pgprot_t prot, unsigned domid);
> > > +                        pgprot_t prot, unsigned domid,
> > > +                        struct xen_pvh_pfn_info *pvhp);
> > > +int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
> > > +                        struct xen_pvh_pfn_info *pvhp);
> > > +
> > > +struct xen_pvh_pfn_info {
> > 
> > Can we call this xen_remap_mfn_info or something? PVH is x86 specific
> > while this struct is also useful on ARM.
> 
> I already renamed it to: xen_xlat_pfn_info.

What does xlat refer to here? I don't think we translate anything with
this struct.

> > > + struct page **pi_paga;          /* pfn info page
> > > array */
> > 
> > can we just call this "pages"? paga is pretty meaningless.
> 
> page array! i can rename page_array or page_a.

What's wrong with pages? It's short (some of the lines using this stuff
are necessarily pretty long) and obvious.

> > > + int           pi_num_pgs;
> > > + int           pi_next_todo;
> > 
> > I don't think we need the pi_ prefix for any of these.
> 
> The prefix for fields in struct make it easy to find via cscope or
> grep, otherwise, it's a nightmare to find common field names like
> pages when reading code. I really get frustrated. I prefer prefixing
> all field names.

It's not common practice in Linux to do so but fair enough.

While implementing the ARM version of this interface it occurred to me
that the num_pgs and next_todo fields here are not really needed across
the arch interface e.g. you already get pi_num_pgs from the nr argument
to xen_remap_domain_mfn_range and pi_next_todo is really state which
fits in struct pvh_remap_data. That would mean that remap_foo could take
a struct page * directly and I think you would save an allocation.

I may look into implementing that change as I code up the ARM side.

Ian.


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