domctl: fix IRQ permission granting/revocation

Commit 545607eb3c ("x86: fix various issues with handling guest IRQs")
wasn't really consistent in one respect: The granting of access to an
IRQ shouldn't assume the pIRQ->IRQ translation to be the same in both
domains. In fact it is wrong to assume that a translation is already/
still in place at the time access is being granted/revoked.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -981,18 +981,18 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xe
 
     case XEN_DOMCTL_irq_permission:
     {
-        unsigned int pirq = op->u.irq_permission.pirq;
+        unsigned int pirq = op->u.irq_permission.pirq, irq;
         int allow = op->u.irq_permission.allow_access;
 
         if ( pirq >= d->nr_pirqs )
             ret = -EINVAL;
-        else if ( !pirq_access_permitted(current->domain, pirq) ||
+        else if ( !(irq = pirq_access_permitted(current->domain, pirq)) ||
                   xsm_irq_permission(XSM_HOOK, d, pirq, allow) )
             ret = -EPERM;
         else if ( allow )
-            ret = pirq_permit_access(d, pirq);
+            ret = irq_permit_access(d, irq);
         else
-            ret = pirq_deny_access(d, pirq);
+            ret = irq_deny_access(d, irq);
     }
     break;
 
--- a/xen/include/xen/iocap.h
+++ b/xen/include/xen/iocap.h
@@ -28,22 +28,11 @@
 #define irq_access_permitted(d, i)                      \
     rangeset_contains_singleton((d)->irq_caps, i)
 
-#define pirq_permit_access(d, i) ({                     \
-    struct domain *d__ = (d);                           \
-    int i__ = domain_pirq_to_irq(d__, i);               \
-    i__ > 0 ? rangeset_add_singleton(d__->irq_caps, i__)\
-            : -EINVAL;                                  \
-})
-#define pirq_deny_access(d, i) ({                       \
-    struct domain *d__ = (d);                           \
-    int i__ = domain_pirq_to_irq(d__, i);               \
-    i__ > 0 ? rangeset_remove_singleton(d__->irq_caps, i__)\
-            : -EINVAL;                                  \
-})
 #define pirq_access_permitted(d, i) ({                  \
     struct domain *d__ = (d);                           \
-    rangeset_contains_singleton(d__->irq_caps,          \
-                                domain_pirq_to_irq(d__, i));\
+    int irq__ = domain_pirq_to_irq(d__, i);             \
+    irq__ > 0 && irq_access_permitted(d__, irq__)       \
+    ? irq__ : 0;                                        \
 })
 
 #endif /* __XEN_IOCAP_H__ */