[Qemu-devel] [PATCH v3 6/8] migration/ram: ensure write persistence on loading normal pages to PMEM

[Haozhong Zhang]

When loading a normal page to persistent memory, load its data by
libpmem function pmem_memcpy_nodrain() instead of memcpy(). Combined
with a call to pmem_drain() at the end of memory loading, we can
guarantee all those normal pages are persistenly loaded to PMEM.

Signed-off-by: Haozhong Zhang <address@hidden>
---
 include/migration/qemu-file-types.h |  2 ++
 include/qemu/pmem.h                 |  1 +
 migration/qemu-file.c               | 29 +++++++++++++++++++----------
 migration/ram.c                     |  2 +-
 stubs/pmem.c                        |  5 +++++
 tests/Makefile.include              |  2 +-
 6 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/include/migration/qemu-file-types.h 
b/include/migration/qemu-file-types.h
index bd6d7dd7f9..c7c3f665f9 100644
--- a/include/migration/qemu-file-types.h
+++ b/include/migration/qemu-file-types.h
@@ -33,6 +33,8 @@ void qemu_put_byte(QEMUFile *f, int v);
 void qemu_put_be16(QEMUFile *f, unsigned int v);
 void qemu_put_be32(QEMUFile *f, unsigned int v);
 void qemu_put_be64(QEMUFile *f, uint64_t v);
+size_t qemu_get_buffer_common(QEMUFile *f, uint8_t *buf, size_t size,
+                              bool is_pmem);
 size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t size);
 
 int qemu_get_byte(QEMUFile *f);
diff --git a/include/qemu/pmem.h b/include/qemu/pmem.h
index ce96379f3c..127b87c326 100644
--- a/include/qemu/pmem.h
+++ b/include/qemu/pmem.h
@@ -16,6 +16,7 @@
 #include <libpmem.h>
 #else  /* !CONFIG_LIBPMEM */
 
+void *pmem_memcpy_nodrain(void *pmemdest, const void *src, size_t len);
 void *pmem_memcpy_persist(void *pmemdest, const void *src, size_t len);
 void *pmem_memset_nodrain(void *pmemdest, int c, size_t len);
 void pmem_drain(void);
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 2ab2bf362d..d19f677796 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -26,6 +26,7 @@
 #include "qemu-common.h"
 #include "qemu/error-report.h"
 #include "qemu/iov.h"
+#include "qemu/pmem.h"
 #include "migration.h"
 #include "qemu-file.h"
 #include "trace.h"
@@ -471,18 +472,13 @@ size_t qemu_peek_buffer(QEMUFile *f, uint8_t **buf, 
size_t size, size_t offset)
     return size;
 }
 
-/*
- * Read 'size' bytes of data from the file into buf.
- * 'size' can be larger than the internal buffer.
- *
- * It will return size bytes unless there was an error, in which case it will
- * return as many as it managed to read (assuming blocking fd's which
- * all current QEMUFile are)
- */
-size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t size)
+size_t qemu_get_buffer_common(QEMUFile *f, uint8_t *buf, size_t size,
+                              bool is_pmem)
 {
     size_t pending = size;
     size_t done = 0;
+    void *(*memcpy_func)(void *d, const void *s, size_t n) =
+        is_pmem ? pmem_memcpy_nodrain : memcpy;
 
     while (pending > 0) {
         size_t res;
@@ -492,7 +488,7 @@ size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t 
size)
         if (res == 0) {
             return done;
         }
-        memcpy(buf, src, res);
+        memcpy_func(buf, src, res);
         qemu_file_skip(f, res);
         buf += res;
         pending -= res;
@@ -501,6 +497,19 @@ size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t 
size)
     return done;
 }
 
+/*
+ * Read 'size' bytes of data from the file into buf.
+ * 'size' can be larger than the internal buffer.
+ *
+ * It will return size bytes unless there was an error, in which case it will
+ * return as many as it managed to read (assuming blocking fd's which
+ * all current QEMUFile are)
+ */
+size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t size)
+{
+    return qemu_get_buffer_common(f, buf, size, false);
+}
+
 /*
  * Read 'size' bytes of data from the file.
  * 'size' can be larger than the internal buffer.
diff --git a/migration/ram.c b/migration/ram.c
index cb93f9fafe..96f33018cf 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2944,7 +2944,7 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
             break;
 
         case RAM_SAVE_FLAG_PAGE:
-            qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
+            qemu_get_buffer_common(f, host, TARGET_PAGE_SIZE, is_pmem);
             break;
 
         case RAM_SAVE_FLAG_COMPRESS_PAGE:
diff --git a/stubs/pmem.c b/stubs/pmem.c
index a65b3bfc6b..e172f31174 100644
--- a/stubs/pmem.c
+++ b/stubs/pmem.c
@@ -26,3 +26,8 @@ void *pmem_memset_nodrain(void *pmemdest, int c, size_t len)
 void pmem_drain(void)
 {
 }
+
+void *pmem_memcpy_nodrain(void *pmemdest, const void *src, size_t len)
+{
+    return memcpy(pmemdest, src, len);
+}
diff --git a/tests/Makefile.include b/tests/Makefile.include
index a1bcbffe12..9ffb0cf8eb 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -637,7 +637,7 @@ tests/test-qdev-global-props$(EXESUF): 
tests/test-qdev-global-props.o \
        $(test-qapi-obj-y)
 tests/test-vmstate$(EXESUF): tests/test-vmstate.o \
        migration/vmstate.o migration/vmstate-types.o migration/qemu-file.o \
-        migration/qemu-file-channel.o migration/qjson.o \
+        migration/qemu-file-channel.o migration/qjson.o stubs/pmem.o \
        $(test-io-obj-y)
 tests/test-timed-average$(EXESUF): tests/test-timed-average.o 
$(test-util-obj-y)
 tests/test-base64$(EXESUF): tests/test-base64.o $(test-util-obj-y)
-- 
2.16.1