[PATCH v2] domctl: fix IRQ permission granting/revocation

["Jan Beulich" <JBeulich@suse.com>]

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.

What is wanted is to translate the incoming pIRQ to an IRQ for
the invoking domain (as the pIRQ is the only notion the invoking
domain has of the IRQ), and grant the subject domain access to
the resulting IRQ.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: Also fix initial range check to use current->domain, adjust code
    structure, and extend description (all requested by Ian). Along
    the lines of the first mentioned change, also pass the Xen IRQ
    number to the XSM hook (confirmed okay by Daniel).
Note that I would hope for this to make unnecessary Stefano's proposed
tools side change
http://lists.xenproject.org/archives/html/xen-devel/2014-12/msg00160.html.

--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -982,18 +982,21 @@ 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 )
+        if ( pirq >= current->domain->nr_pirqs )
+        {
             ret = -EINVAL;
-        else if ( !pirq_access_permitted(current->domain, pirq) ||
-                  xsm_irq_permission(XSM_HOOK, d, pirq, allow) )
+            break;
+        }
+        irq = pirq_access_permitted(current->domain, pirq);
+        if ( !irq || xsm_irq_permission(XSM_HOOK, d, irq, 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__ */