x86: fix guest CPUID handling

The way XEN_DOMCTL_set_cpuid got handled so far allowed for surprises
to the caller. With this set of operations
- set leaf A (using array index 0)
- set leaf B (using array index 1)
- clear leaf A (clearing array index 0)
- set leaf B (using array index 0)
- clear leaf B (clearing array index 0)
the entry for leaf B at array index 1 would still be in place, while
the caller would expect it to be cleared.

While looking at the use sites of d->arch.cpuid[] I also noticed that
the allocation of the array needlessly uses the zeroing form - the
relevant fields of the array elements get set in a loop immediately
following the allocation.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>
master commit: 4c0ff6bd54b5a67f8f820f9ed0a89a79f1a26a1c
master date: 2014-05-02 12:09:03 +0200

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index fdf550fb7af11a51095a4a2ef9cce0e0c2fc70c7..8f11473afe85149da4366ea32f9bbdb4ba828100 100644 (file)
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -609,7 +609,7 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags)
 
     if ( !is_idle_domain(d) )
     {
-        d->arch.cpuids = xzalloc_array(cpuid_input_t, MAX_CPUID_INPUT);
+        d->arch.cpuids = xmalloc_array(cpuid_input_t, MAX_CPUID_INPUT);
         rc = -ENOMEM;
         if ( d->arch.cpuids == NULL )
             goto fail;

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 63e19879e490629590af6613b06f97ac705714a5..099fb4b75f73c6675ba4fa0e374c7f251fb332fe 100644 (file)
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -1154,7 +1154,7 @@ long arch_do_domctl(
     {
         struct domain *d;
         xen_domctl_cpuid_t *ctl = &domctl->u.cpuid;
-        cpuid_input_t *cpuid = NULL; 
+        cpuid_input_t *cpuid, *unused = NULL;
         int i;
 
         ret = -ESRCH;
@@ -1162,12 +1162,16 @@ long arch_do_domctl(
         if ( d == NULL )
             break;
 
-        for ( i = 0; i < MAX_CPUID_INPUT; i++ )
+        for ( ret = i = 0; i < MAX_CPUID_INPUT; i++ )
         {
             cpuid = &d->arch.cpuids[i];
 
             if ( cpuid->input[0] == XEN_CPUID_INPUT_UNUSED )
-                break;
+            {
+                if ( !unused )
+                    unused = cpuid;
+                continue;
+            }
 
             if ( (cpuid->input[0] == ctl->input[0]) &&
                  ((cpuid->input[1] == XEN_CPUID_INPUT_UNUSED) ||
@@ -1175,15 +1179,12 @@ long arch_do_domctl(
                 break;
         }
         
-        if ( i == MAX_CPUID_INPUT )
-        {
-            ret = -ENOENT;
-        }
+        if ( i < MAX_CPUID_INPUT )
+            *cpuid = *ctl;
+        else if ( unused )
+            *unused = *ctl;
         else
-        {
-            memcpy(cpuid, ctl, sizeof(cpuid_input_t));
-            ret = 0;
-        }
+            ret = -ENOENT;
 
         rcu_unlock_domain(d);
     }