Re: [V6 PATCH 6.1/7] pvh dom0: Add and remove foreign pages

[Mukesh Rathor <mukesh.rathor@oracle.com>]

On Mon, 09 Dec 2013 09:50:28 +0000
"Jan Beulich" <JBeulich@suse.com> wrote:

> >>> On 07.12.13 at 03:34, Mukesh Rathor <mukesh.rathor@oracle.com>
> >>> wrote:
> > New version of the patch with xenmem_rem_foreign_from_p2m() created:
> > 
> > In this patch, a new function, xenmem_add_foreign_to_p2m(), is added
> > to map pages from foreign guest into current dom0 for domU creation.
> > Such pages are typed p2m_map_foreign. Another function
> > xenmem_rem_foreign_from_p2m() is added to remove such pages. Note,
> > in the remove path, we must release the refcount that was taken
> > during the map phase.
> 
> Wouldn't both of the new functions better go into arch/x86/mm/p2m.c
> (as already reflected by the declaration of the one that's currently
> not static being placed in p2m.h)? In any event, the p2m interaction
> here needs Tim's blessing.

ok, i can move them to p2m.c, perhaps rename to p2m_add_foreign...

> > +/* Note, the refcnt released here is taken in
> > xenmem_add_foreign_to_p2m */ +int
> > xenmem_rem_foreign_from_p2m(struct domain *d, unsigned long gpfn) +{
> > +    unsigned long mfn;
> > +    p2m_type_t p2mt;
> > +    struct domain *foreign_dom;
> > +
> > +    mfn = mfn_x(get_gfn_query(d, gpfn, &p2mt));
> > +    if ( !mfn_valid(mfn) )
> > +    {
> > +        gdprintk(XENLOG_WARNING, "Invalid mfn for gpfn:%lx
> > domid:%d\n",
> > +                 gpfn, d->domain_id);
> > +        return -EINVAL;
> > +    }
> 
> ASSERT(p2m_is_foreign(p2mt)) ?

Called for foreign only, but good idea to check for it in case of
other callers in future.

> > +
> > +    foreign_dom = page_get_owner(mfn_to_page(mfn));
> > +    ASSERT(d != foreign_dom);
> > +    ASSERT(is_pvh_domain(d));
> 
> Wouldn't this better be done first thing in the function?

ok.