pc: limit DIMM address and size to page aligned values

When running in KVM mode, kvm_set_phys_mem() will silently
fail if registered MemoryRegion address/size is not page
aligned. Causing memory hotplug failure in guest.

Mapping non aligned MemoryRegion in TCG mode 'works', but
sane guest OS still expects page aligned memory module
and fails to initialize it if it's not aligned.

So do not allow non aligned (i.e. valid) address/size
values for DIMM to avoid either KVM failure or guest
issues caused by it.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/i386/pc.c

@@ -1556,6 +1556,7 @@ static void pc_dimm_plug(HotplugHandler *hotplug_dev,
     PCDIMMDevice *dimm = PC_DIMM(dev);
     PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
     MemoryRegion *mr = ddc->get_memory_region(dimm);
+    uint64_t align = TARGET_PAGE_SIZE;
     uint64_t addr;
 
     addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP, &local_err);
@@ -1565,7 +1566,7 @@ static void pc_dimm_plug(HotplugHandler *hotplug_dev,
 
     addr = pc_dimm_get_free_addr(pcms->hotplug_memory_base,
                                  memory_region_size(&pcms->hotplug_memory),
-                                 !addr ? NULL : &addr,
+                                 !addr ? NULL : &addr, align,
                                  memory_region_size(mr), &local_err);
     if (local_err) {
         goto out;

hw/mem/pc-dimm.c

@@ -139,7 +139,7 @@ static int pc_dimm_built_list(Object *obj, void *opaque)
 
 uint64_t pc_dimm_get_free_addr(uint64_t address_space_start,
                                uint64_t address_space_size,
-                               uint64_t *hint, uint64_t size,
+                               uint64_t *hint, uint64_t align, uint64_t size,
                                Error **errp)
 {
     GSList *list = NULL, *item;
@@ -152,6 +152,18 @@ uint64_t pc_dimm_get_free_addr(uint64_t address_space_start,
         goto out;
     }
 
+    if (hint && QEMU_ALIGN_UP(*hint, align) != *hint) {
+        error_setg(errp, "address must be aligned to 0x%" PRIx64 " bytes",
+                   align);
+        goto out;
+    }
+
+    if (QEMU_ALIGN_UP(size, align) != size) {
+        error_setg(errp, "backend memory size must be multiple of 0x%"
+                   PRIx64, align);
+        goto out;
+    }
+
     assert(address_space_end > address_space_start);
     object_child_foreach(qdev_get_machine(), pc_dimm_built_list, &list);
 

include/hw/mem/pc-dimm.h

@@ -72,7 +72,7 @@ typedef struct PCDIMMDeviceClass {
 
 uint64_t pc_dimm_get_free_addr(uint64_t address_space_start,
                                uint64_t address_space_size,
-                               uint64_t *hint, uint64_t size,
+                               uint64_t *hint, uint64_t align, uint64_t size,
                                Error **errp);
 
 int pc_dimm_get_free_slot(const int *hint, int max_slots, Error **errp);