patch-0001-xen-move-domain-lookup-for-getdomaininfo-to-the-same.patch

From ebddda4de8c95412f4d722d341540ae54d998a94 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Thu, 23 Jun 2016 14:14:06 +0200
Subject: [PATCH 1/2] xen: move domain lookup for getdomaininfo to the same
 place as others
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Organization: Invisible Things Lab
Cc: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

XEN_DOMCTL_getdomaininfo have different semantics than most of others
domctls - it returns information about first valid domain with ID >=
argument. But that's no excuse for having the lookup code in a different
place, which made handling different corner cases unnecessary complex.
Move the lookup to the first switch clause. And adjust locking to be the
same as for other cases.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 xen/common/domctl.c | 41 ++++++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index e43904e..6ae1fe0 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -442,11 +442,29 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
     switch ( op->cmd )
     {
     case XEN_DOMCTL_createdomain:
-    case XEN_DOMCTL_getdomaininfo:
     case XEN_DOMCTL_test_assign_device:
     case XEN_DOMCTL_gdbsx_guestmemio:
         d = NULL;
         break;
+    case XEN_DOMCTL_getdomaininfo:
+        d = rcu_lock_domain_by_id(op->domain);
+        if ( d == NULL )
+        {
+            /* search for the next valid domain */
+            rcu_read_lock(&domlist_read_lock);
+
+            for_each_domain ( d )
+                if ( d->domain_id >= op->domain )
+                {
+                    rcu_lock_domain(d);
+                    break;
+                }
+
+            rcu_read_unlock(&domlist_read_lock);
+            if ( d == NULL )
+                return -ESRCH;
+        }
+        break;
     default:
         d = rcu_lock_domain_by_id(op->domain);
         if ( d == NULL )
@@ -862,33 +880,14 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
         break;
 
     case XEN_DOMCTL_getdomaininfo:
-    {
-        domid_t dom = op->domain;
-
-        rcu_read_lock(&domlist_read_lock);
-
-        for_each_domain ( d )
-            if ( d->domain_id >= dom )
-                break;
-
-        ret = -ESRCH;
-        if ( d == NULL )
-            goto getdomaininfo_out;
-
         ret = xsm_getdomaininfo(XSM_HOOK, d);
         if ( ret )
-            goto getdomaininfo_out;
+            break;
 
         getdomaininfo(d, &op->u.getdomaininfo);
-
         op->domain = op->u.getdomaininfo.domain;
         copyback = 1;
-
-    getdomaininfo_out:
-        rcu_read_unlock(&domlist_read_lock);
-        d = NULL;
         break;
-    }
 
     case XEN_DOMCTL_getvcpucontext:
     {
-- 
2.5.5