[Qemu-devel] [PATCH v4 4/8] mem/nvdimm: ensure write persistence to PMEM in label emulation

[Haozhong Zhang]

Guest writes to vNVDIMM labels are intercepted and performed on the
backend by QEMU. When the backend is a real persistent memort, QEMU
needs to take proper operations to ensure its write persistence on the
persistent memory. Otherwise, a host power failure may result in the
loss of guest label configurations.

Signed-off-by: Haozhong Zhang <address@hidden>
---
 hw/mem/nvdimm.c     |  9 ++++++++-
 include/qemu/pmem.h | 23 +++++++++++++++++++++++
 stubs/Makefile.objs |  1 +
 stubs/pmem.c        | 19 +++++++++++++++++++
 4 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 include/qemu/pmem.h
 create mode 100644 stubs/pmem.c

diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
index 61e677f92f..18861d1a7a 100644
--- a/hw/mem/nvdimm.c
+++ b/hw/mem/nvdimm.c
@@ -23,6 +23,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/pmem.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
 #include "qapi-visit.h"
@@ -156,11 +157,17 @@ static void nvdimm_write_label_data(NVDIMMDevice *nvdimm, 
const void *buf,
 {
     MemoryRegion *mr;
     PCDIMMDevice *dimm = PC_DIMM(nvdimm);
+    bool is_pmem = object_property_get_bool(OBJECT(dimm->hostmem),
+                                            "pmem", NULL);
     uint64_t backend_offset;
 
     nvdimm_validate_rw_label_data(nvdimm, size, offset);
 
-    memcpy(nvdimm->label_data + offset, buf, size);
+    if (!is_pmem) {
+        memcpy(nvdimm->label_data + offset, buf, size);
+    } else {
+        pmem_memcpy_persist(nvdimm->label_data + offset, buf, size);
+    }
 
     mr = host_memory_backend_get_memory(dimm->hostmem, &error_abort);
     backend_offset = memory_region_size(mr) - nvdimm->label_size + offset;
diff --git a/include/qemu/pmem.h b/include/qemu/pmem.h
new file mode 100644
index 0000000000..16f5b2653a
--- /dev/null
+++ b/include/qemu/pmem.h
@@ -0,0 +1,23 @@
+/*
+ * QEMU header file for libpmem.
+ *
+ * Copyright (c) 2018 Intel Corporation.
+ *
+ * Author: Haozhong Zhang <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef QEMU_PMEM_H
+#define QEMU_PMEM_H
+
+#ifdef CONFIG_LIBPMEM
+#include <libpmem.h>
+#else  /* !CONFIG_LIBPMEM */
+
+void *pmem_memcpy_persist(void *pmemdest, const void *src, size_t len);
+
+#endif /* CONFIG_LIBPMEM */
+
+#endif /* !QEMU_PMEM_H */
diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index 2d59d84091..ba944b9739 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -43,3 +43,4 @@ stub-obj-y += xen-common.o
 stub-obj-y += xen-hvm.o
 stub-obj-y += pci-host-piix.o
 stub-obj-y += ram-block.o
+stub-obj-$(call lnot,$(CONFIG_LIBPMEM)) += pmem.o
\ No newline at end of file
diff --git a/stubs/pmem.c b/stubs/pmem.c
new file mode 100644
index 0000000000..03d990e571
--- /dev/null
+++ b/stubs/pmem.c
@@ -0,0 +1,19 @@
+/*
+ * Stubs for libpmem.
+ *
+ * Copyright (c) 2018 Intel Corporation.
+ *
+ * Author: Haozhong Zhang <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <string.h>
+
+#include "qemu/pmem.h"
+
+void *pmem_memcpy_persist(void *pmemdest, const void *src, size_t len)
+{
+    return memcpy(pmemdest, src, len);
+}
-- 
2.14.1