[libvirt] Error when creating VM with persistent memory

[Michal Privoznik]

On 8/27/19 9:58 AM, Seema Pandit wrote:
> error: internal error: qemu unexpectedly closed the monitor: ftruncate:
> Invalid argument 2019-08-22T04:16:08.744402Z qemu-system-x86_64: -object
> memory-backend-file,id=memnvdimm0,prealloc=yes,mem-path=/dev/dax1.0,size=403726925824:
> unable to map backing store for guest RAM: Cannot allocate memory

I wonder if dropping 'prealloc' would help. This error message comes 
from phase before 'prealloc' is processed. You can try the following 
patch:


diff --git i/src/qemu/qemu_command.c w/src/qemu/qemu_command.c
index 373ebd6d1a..c375955eab 100644
--- i/src/qemu/qemu_command.c
+++ w/src/qemu/qemu_command.c
@@ -3468,7 +3468,7 @@ qemuBuildMemoryBackendProps(virJSONValuePtr *backendProps,
         }
 
         if (virJSONValueObjectAdd(props,
-                                  "B:prealloc", prealloc,
+                                  "B:prealloc", prealloc ? false : false,
                                   "s:mem-path", memPath,
                                   NULL) < 0)
             goto cleanup;

Michal