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[Qemu-devel] [PATCH v2 4/8] mem/nvdimm: ensure write persistence to PMEM


From: Haozhong Zhang
Subject: [Qemu-devel] [PATCH v2 4/8] mem/nvdimm: ensure write persistence to PMEM in label emulation
Date: Wed, 7 Feb 2018 15:33:27 +0800

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 | 31 +++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 include/qemu/pmem.h

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..9017596ff0
--- /dev/null
+++ b/include/qemu/pmem.h
@@ -0,0 +1,31 @@
+/*
+ * Stub functions 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 */
+
+#include <string.h>
+
+/* Stubs */
+
+static inline void *
+pmem_memcpy_persist(void *pmemdest, const void *src, size_t len)
+{
+    return memcpy(pmemdest, src, len);
+}
+
+#endif /* CONFIG_LIBPMEM */
+
+#endif /* !QEMU_PMEM_H */
-- 
2.14.1




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