1 files changed, 56 insertions, 9 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index f77e499afddd..065f0b607373 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -257,10 +257,25 @@ static void release_memory_resource(struct resource *resource)
         kfree(resource);
 }
 
+/*
+ * Host memory not allocated to dom0. We can use this range for hotplug-based
+ * ballooning.
+ *
+ * It's a type-less resource. Setting IORESOURCE_MEM will make resource
+ * management algorithms (arch_remove_reservations()) look into guest e820,
+ * which we don't want.
+ */
+static struct resource hostmem_resource = {
+        .name   = "Host RAM",
+};
+
+void __attribute__((weak)) __init arch_xen_balloon_init(struct resource *res)
+{}
+
 static struct resource *additional_memory_resource(phys_addr_t size)
 {
-        struct resource *res;
-        int ret;
+        struct resource *res, *res_hostmem;
+        int ret = -ENOMEM;
 
         res = kzalloc(sizeof(*res), GFP_KERNEL);
         if (!res)
@@ -269,13 +284,42 @@ static struct resource *additional_memory_resource(phys_addr_t size)
         res->name = "System RAM";
         res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
-        ret = allocate_resource(&iomem_resource, res,
-                                size, 0, -1,
-                                PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
-        if (ret < 0) {
-                pr_err("Cannot allocate new System RAM resource\n");
-                kfree(res);
-                return NULL;
+        res_hostmem = kzalloc(sizeof(*res), GFP_KERNEL);
+        if (res_hostmem) {
+                /* Try to grab a range from hostmem */
+                res_hostmem->name = "Host memory";
+                ret = allocate_resource(&hostmem_resource, res_hostmem,
+                                        size, 0, -1,
+                                        PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
+        }
+
+        if (!ret) {
+                /*
+                 * Insert this resource into iomem. Because hostmem_resource
+                 * tracks portion of guest e820 marked as UNUSABLE noone else
+                 * should try to use it.
+                 */
+                res->start = res_hostmem->start;
+                res->end = res_hostmem->end;
+                ret = insert_resource(&iomem_resource, res);
+                if (ret < 0) {
+                        pr_err("Can't insert iomem_resource [%llx - %llx]\n",
+                                res->start, res->end);
+                        release_memory_resource(res_hostmem);
+                        res_hostmem = NULL;
+                        res->start = res->end = 0;
+                }
+        }
+
+        if (ret) {
+                ret = allocate_resource(&iomem_resource, res,
+                                        size, 0, -1,
+                                        PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
+                if (ret < 0) {
+                        pr_err("Cannot allocate new System RAM resource\n");
+                        kfree(res);
+                        return NULL;
+                }
         }
 
 #ifdef CONFIG_SPARSEMEM
@@ -287,6 +331,7 @@ static struct resource *additional_memory_resource(phys_addr_t size)
                         pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n",
                                pfn, limit);
                         release_memory_resource(res);
+                        release_memory_resource(res_hostmem);
                         return NULL;
                 }
         }
@@ -765,6 +810,8 @@ static int __init balloon_init(void)
         set_online_page_callback(&xen_online_page);
         register_memory_notifier(&xen_memory_nb);
         register_sysctl_table(xen_root);
+
+        arch_xen_balloon_init(&hostmem_resource);
 #endif
 
 #ifdef CONFIG_XEN_PV