hostmem: detect host backend memory is being used properly

Currently, we use memory_region_is_mapped() to detect if the host
backend memory is being used. This works if the memory is directly
mapped into guest's address space, however, it is not true for
nvdimm as it uses aliased memory region to map the memory. This is
why this bug can happen:
   https://bugzilla.redhat.com/show_bug.cgi?id=1352769

Fix it by introduce a new filed, is_mapped, to HostMemoryBackend,
we set/clear this filed accordingly when the device link/unlink to
host backend memory

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index c4dde3a52e..7e7c843b32 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -1008,10 +1008,7 @@ static const TypeInfo ivshmem_common_info = {
 static void ivshmem_check_memdev_is_busy(Object *obj, const char *name,
                                          Object *val, Error **errp)
 {
-    MemoryRegion *mr;
-
-    mr = host_memory_backend_get_memory(MEMORY_BACKEND(val), &error_abort);
-    if (memory_region_is_mapped(mr)) {
+    if (host_memory_backend_is_mapped(MEMORY_BACKEND(val))) {
         char *path = object_get_canonical_path_component(val);
         error_setg(errp, "can't use already busy memdev: %s", path);
         g_free(path);
@@ -1060,6 +1057,14 @@ static void ivshmem_plain_realize(PCIDevice *dev, Error **errp)
     }
 
     ivshmem_common_realize(dev, errp);
+    host_memory_backend_set_mapped(s->hostmem, true);
+}
+
+static void ivshmem_plain_exit(PCIDevice *pci_dev)
+{
+    IVShmemState *s = IVSHMEM_COMMON(pci_dev);
+
+    host_memory_backend_set_mapped(s->hostmem, false);
 }
 
 static void ivshmem_plain_class_init(ObjectClass *klass, void *data)
@@ -1068,6 +1073,7 @@ static void ivshmem_plain_class_init(ObjectClass *klass, void *data)
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
     k->realize = ivshmem_plain_realize;
+    k->exit = ivshmem_plain_exit;
     dc->props = ivshmem_plain_properties;
     dc->vmsd = &ivshmem_plain_vmsd;
 }