exec: Fix Xen RAM allocation with unusual options

Issues:

* We try to obey -mem-path even though it can't work with Xen.

* To implement -machine mem-merge, we call
  memory_try_enable_merging(new_block->host, size).  But with Xen,
  new_block->host remains null.  Oops.

Fix by separating Xen allocation from normal allocation.

Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1375276272-15988-2-git-send-email-armbru@redhat.com
Signed-off-by: Anthony Liguori <anthony@codemonkey.ws>

exec.c

diff --git a/exec.c b/exec.c
index 030118e..da1d388 100644
--- a/exec.c
+++ b/exec.c
@@ -1107,6 +1107,12 @@
     if (host) {
         new_block->host = host;
         new_block->flags |= RAM_PREALLOC_MASK;
+    } else if (xen_enabled()) {
+        if (mem_path) {
+            fprintf(stderr, "-mem-path not supported with Xen\n");
+            exit(1);
+        }
+        xen_ram_alloc(new_block->offset, size, mr);
     } else {
         if (mem_path) {
 #if defined (__linux__) && !defined(TARGET_S390X)
@@ -1120,9 +1126,7 @@
             exit(1);
 #endif
         } else {
-            if (xen_enabled()) {
-                xen_ram_alloc(new_block->offset, size, mr);
-            } else if (kvm_enabled()) {
+            if (kvm_enabled()) {
                 /* some s390/kvm configurations have special constraints */
                 new_block->host = kvm_ram_alloc(size);
             } else {
@@ -1200,6 +1204,8 @@
             ram_list.version++;
             if (block->flags & RAM_PREALLOC_MASK) {
                 ;
+            } else if (xen_enabled()) {
+                xen_invalidate_map_cache_entry(block->host);
             } else if (mem_path) {
 #if defined (__linux__) && !defined(TARGET_S390X)
                 if (block->fd) {
@@ -1212,11 +1218,7 @@
                 abort();
 #endif
             } else {
-                if (xen_enabled()) {
-                    xen_invalidate_map_cache_entry(block->host);
-                } else {
-                    qemu_anon_ram_free(block->host, block->length);
-                }
+                qemu_anon_ram_free(block->host, block->length);
             }
             g_free(block);
             break;
@@ -1240,6 +1242,8 @@
             vaddr = block->host + offset;
             if (block->flags & RAM_PREALLOC_MASK) {
                 ;
+            } else if (xen_enabled()) {
+                abort();
             } else {
                 flags = MAP_FIXED;
                 munmap(vaddr, length);