Re: [Xen-devel] [RFC PATCH 13/16]: PVH xen: introduce p2m_map_foreign

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Thu, 24 Jan 2013 17:18:15 +0000
Tim Deegan <tim@xxxxxxx> wrote:

> At 18:09 -0800 on 11 Jan (1357927784), Mukesh Rathor wrote:
> > @@ -584,6 +584,11 @@ guest_physmap_add_entry(struct domain *d
> >          {
> >              ASSERT(mfn_valid(omfn));
> >              set_gpfn_from_mfn(mfn_x(omfn), INVALID_M2P_ENTRY);
> > +
> > +            /* Because PVH domU uses kmalloc for grant pfn, we
> > need to save
> > +             * and restore the old mfn */
> > +             if (is_pvh_domain(d) && p2m_is_grant(t))
> > +                 free_domheap_page(mfn_to_page(omfn));
> 
> I think you'll need to explain this in more detail.  The comment
> assumes that the guest is running linux, which is worrying.  And in
> any case you can't just free_domheap_page() the guest's memory!  What
> if another domain has a reference to it?

Ok, I fixed linux side so instead of kmalloc it uses ballooning to
get pfn space for the grant table. That means there should not be 
an omfn here. If there is, I think I should just fail the operation, 
ie, guest_physmap_add_entry(), right?

thanks,
Mukesh


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