xen: only track the linear framebuffer

Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track anything but the vga vram region.
Signed-off-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>

xen-all.c

@@ -215,6 +215,7 @@ static int xen_add_to_physmap(XenIOState *state,
     int rc = 0;
     XenPhysmap *physmap = NULL;
     target_phys_addr_t pfn, start_gpfn;
+    RAMBlock *block;
 
     if (get_physmapping(state, start_addr, size)) {
         return 0;
@@ -223,6 +224,19 @@ static int xen_add_to_physmap(XenIOState *state,
         return -1;
     }
 
+    /* Xen can only handle a single dirty log region for now and we want
+     * the linear framebuffer to be that region.
+     * Avoid tracking any regions that is not videoram and avoid tracking
+     * the legacy vga region. */
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        if (!strcmp(block->idstr, "vga.vram") && block->offset == phys_offset
+                && start_addr > 0xbffff) {
+            goto go_physmap;
+        }
+    }
+    return -1;
+
+go_physmap:
     DPRINTF("mapping vram to %llx - %llx, from %llx\n",
             start_addr, start_addr + size, phys_offset);