Re: [PATCH 14/18 V2]: PVH xen: add xenmem_add_foreign_to_pmap()

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

On Thu, 21 Mar 2013 17:41:46 +0000
Tim Deegan <tim@xen.org> wrote:

> > diff --git a/xen/common/memory.c b/xen/common/memory.c
> > index 68501d1..91a56b6 100644
> > --- a/xen/common/memory.c
> > +++ b/xen/common/memory.c
> > +        /* PVH note: if PVH, the gfn could be mapped to a mfn from
> > foreign
> > +         * domain by the user space tool during domain creation.
> > We need to
> > +         * check for that, free it up from the p2m, and release
> > refcnt on it.
> > +         * In such a case, page would be NULL. */
> > +
> > +        page = get_page_from_gfn(d, xrfp.gpfn, &p2mt, P2M_ALLOC);
> > +        valid_pvh_pg = is_curr_pvh && 
> > +                       (p2m_is_mmio(p2mt) || p2m_is_foreign(p2mt));
> 

Actually, looking at this again, I can't find reason why I can't just change
get_page_from_gfn_p2m() to return page for foreign also:

    if ( likely(!p2m_locked_by_me(p2m)) )
    {   
        /* Fast path: look up and get out */
        p2m_read_lock(p2m);
        mfn = __get_gfn_type_access(p2m, gfn, t, a, 0, NULL, 0);
        if ( (p2m_is_ram(*t) || p2m_is_grant(*t) || p2m_is_foreign(*t)) <====
             && mfn_valid(mfn)
             && !((q & P2M_UNSHARE) && p2m_is_shared(*t)) )
        {
            page = mfn_to_page(mfn);
            if ( !get_page(page, d)
                 /* Page could be shared */
                 && !get_page(page, dom_cow) )
                page = NULL;
        }
......

    /* Slow path: take the write lock and do fixups */
    mfn = get_gfn_type_access(p2m, gfn, t, a, q, NULL);
    if ( p2m_is_ram(*t) && mfn_valid(mfn) ) <=======  Add p2m_is_foreign HERE
    {

Please lmk if you forsee any issues with above.
BTW, in the slow path, why doesn't it check for grant?

Also, I removed the mmio from map, so I can remove from here also.

thanks,
Mukesh