Re: [Xen-devel] [PATCH v2 3/6] xen/arm: implement page reference and grant table functions needed by grant_table.c

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-07-24 at 11:25 +0100, Stefano Stabellini wrote:
> On Mon, 23 Jul 2012, Ian Campbell wrote:
> > On Fri, 2012-07-20 at 16:05 +0100, Stefano Stabellini wrote:
> > > The implementation is strongly "inspired" by their x86 counterparts,
> > > except that we assume paging_mode_external and paging_mode_translate.
> > > 
> > > TODO: read_only mappings and gnttab_mark_dirty.
> > 
> > Can we add ASSERT(0) or BUG() or something on those paths, so it becomes
> > obvious when we start hitting them.
> > 
> > ...
> > 
> > Having read the patch I now see that some of them return errors, but
> > others don't and I think they should do something noisy...
> 
> The only path that is unimplemented is in create_grant_host_mapping, it is
> marked with "XXX", and prints an error message and returns an error.

What about gnttab_mark_dirty?

> 
> 
> > > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> > > index 1832e7f..01a6781 100644
> > > --- a/xen/arch/arm/mm.c
> > > +++ b/xen/arch/arm/mm.c
> > > +                    rc = -ENOMEM;
> > > +                    page = alloc_domheap_page(d, 0);
> > > +                    if ( page == NULL ) {
> > > +                        printk("p2m_populate_ram: failed to allocate 
> > > page\n");
> > 
> > Should be a gdprintk or something, since a guest can indirectly trigger
> > this path.
> 
> yes, good idea.



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