Re: [Xen-devel] [V7 PATCH 5/7] pvh: change xsm_add_to_physmap

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Mon, 10 Feb 2014 15:33:18 +0000
Julien Grall <julien.grall@xxxxxxxxxx> wrote:

> On 02/10/2014 03:27 PM, Ian Campbell wrote:
> > On Mon, 2014-02-10 at 15:16 +0000, Julien Grall wrote:
> >> Hi Ian,
> >>
> >> On 02/10/2014 01:42 PM, Ian Campbell wrote:
> >>> On Sun, 2014-02-09 at 16:51 +0000, Julien Grall wrote:
> >>>> Hello Mukesh,
> >>>>
> >>>> On 30/01/14 01:33, Mukesh Rathor wrote:
> >>>>>>> I'm not sure what you mean:
> >>>>>>>   - the code that Mukesh is adding doesn't have a struct
> >>
> >> For ARM, a call to xc_map_foreign_page will end up to
> >> XENMEM_add_to_physmap_range(XENMAPSPACE_gmfn_foreign).
> >>
> >> For both architecture, you can look at the function
> >> xen_remap_map_domain_mfn_range (implemented differently on ARM and
> >> x86) which is the last function called before going to the
> >> hypervisor.
> >>
> >> If we don't modify the hypercall XENMEM_add_to_physmap, we will
> >> have a add a new way to map Xen page for xentrace & co.
> > 
> > Wouldn't it be incorrect to generically return OK for mapping a
> > DOMID_XEN owned page -- at least something needs to validate that
> > the particular mfn being mapped is supposed to be shared with the
> > guest in question.
> 
> It's already the case. By default a xen heap page doesn't belong to
> DOMID_XEN. Xen has to explicitly call share_xen_page_with_privileged
> guess (see an example in xen/common/trace.c:244) to set DOMID_XEN to
> the given page.


So, how about following:

+++ b/xen/common/domain.c
@@ -484,8 +484,20 @@ struct domain *rcu_lock_domain_by_any_id(domid_t dom)
 
  int rcu_lock_remote_domain_by_id(domid_t dom, struct domain **d)
   {
   -    if ( (*d = rcu_lock_domain_by_id(dom)) == NULL )
   +
   +    if ( (dom == DOMID_XEN && (*d = rcu_lock_domain(dom_xen)) == NULL) ||
   +         (dom != DOMID_XEN && (*d = rcu_lock_domain_by_id(dom)) == NULL) )
   +        return -ESRCH;
   +


Ack/Nack?

Thanks
Mukesh


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