[PATCH 1/2] xsm: add ability to elevate a domain to privileged

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

There are now instances where internal hypervisor logic needs to make resource
allocation calls that are protected by XSM checks. The internal hypervisor logic
is represented a number of system domains which by designed are represented by
non-privileged struct domain instances. To enable these logic blocks to
function correctly but in a controlled manner, this commit introduces a pair
of privilege escalation and demotion functions that will make a system domain
privileged and then remove that privilege.

Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
---
 xen/include/xsm/xsm.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
index e22d6160b5..157e57151e 100644
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -189,6 +189,28 @@ struct xsm_operations {
 #endif
 };
 
+static always_inline int xsm_elevate_priv(struct domain *d)
+{
+    if ( is_system_domain(d) )
+    {
+        d->is_privileged = true;
+        return 0;
+    }
+
+    return -EPERM;
+}
+
+static always_inline int xsm_demote_priv(struct domain *d)
+{
+    if ( is_system_domain(d) )
+    {
+        d->is_privileged = false;
+        return 0;
+    }
+
+    return -EPERM;
+}
+
 #ifdef CONFIG_XSM
 
 extern struct xsm_operations *xsm_ops;
-- 
2.20.1