kvm: make --mem-path memory allocation depend on mmu notifiers

[Marcelo Tosatti <mtosatti@redhat.com>]

Without mmu notifiers usage of hugepages to back guest memory can cause
memory corruption.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


diff --git a/qemu/vl.c b/qemu/vl.c
index d0660ab..49cf066 100644
--- a/qemu/vl.c
+++ b/qemu/vl.c
@@ -4664,6 +4664,11 @@ void *alloc_mem_area(size_t memory, unsigned long *len, const char *path)
     void *area;
     int fd;
 
+    if (!kvm_has_sync_mmu()) {
+        fprintf(stderr, "host lacks mmu notifiers, disabling --mem-path\n");
+        return NULL;
+    }
+
     if (asprintf(&filename, "%s/kvm.XXXXXX", path) == -1)
 	return NULL;