[Qemu-devel] [PATCH 8/9 V5] migration/ram: ensure write persistence on loading xbzrle pages to PMEM

[junyan.he@gmx.com]

From: Junyan He <junyan.he@intel.com>

When loading a xbzrle encoded page to persistent memory, load the data
via libpmem function pmem_memcpy_nodrain() instead of memcpy().
Combined with a call to pmem_drain() at the end of memory loading, we
can guarantee those xbzrle encoded pages are persistently loaded to PMEM.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
---
 migration/ram.c        | 6 +++---
 migration/xbzrle.c     | 8 ++++++--
 migration/xbzrle.h     | 3 ++-
 tests/Makefile.include | 2 +-
 tests/test-xbzrle.c    | 4 ++--
 5 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index e0f3dbc..afe227e 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2441,7 +2441,7 @@ static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
     }
 }
 
-static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
+static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host, bool is_pmem)
 {
     unsigned int xh_len;
     int xh_flags;
@@ -2467,7 +2467,7 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
 
     /* decode RLE */
     if (xbzrle_decode_buffer(loaded_data, xh_len, host,
-                             TARGET_PAGE_SIZE) == -1) {
+                             TARGET_PAGE_SIZE, is_pmem) == -1) {
         error_report("Failed to load XBZRLE page - decode error!");
         return -1;
     }
@@ -3083,7 +3083,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
             break;
 
         case RAM_SAVE_FLAG_XBZRLE:
-            if (load_xbzrle(f, addr, host) < 0) {
+            if (load_xbzrle(f, addr, host, is_pmem) < 0) {
                 error_report("Failed to decompress XBZRLE page at "
                              RAM_ADDR_FMT, addr);
                 ret = -EINVAL;
diff --git a/migration/xbzrle.c b/migration/xbzrle.c
index 1ba482d..ca713c3 100644
--- a/migration/xbzrle.c
+++ b/migration/xbzrle.c
@@ -12,6 +12,7 @@
  */
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
+#include "qemu/pmem.h"
 #include "xbzrle.h"
 
 /*
@@ -126,11 +127,14 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
     return d;
 }
 
-int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen)
+int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen,
+                         bool is_pmem)
 {
     int i = 0, d = 0;
     int ret;
     uint32_t count = 0;
+    void *(*memcpy_func)(void *d, const void *s, size_t n) =
+        is_pmem ? pmem_memcpy_nodrain : memcpy;
 
     while (i < slen) {
 
@@ -167,7 +171,7 @@ int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen)
             return -1;
         }
 
-        memcpy(dst + d, src + i, count);
+        memcpy_func(dst + d, src + i, count);
         d += count;
         i += count;
     }
diff --git a/migration/xbzrle.h b/migration/xbzrle.h
index a0db507..f18f679 100644
--- a/migration/xbzrle.h
+++ b/migration/xbzrle.h
@@ -17,5 +17,6 @@
 int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
                          uint8_t *dst, int dlen);
 
-int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen);
+int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen,
+                         bool is_pmem);
 #endif
diff --git a/tests/Makefile.include b/tests/Makefile.include
index 5c25b9b..23d7162 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -631,7 +631,7 @@ tests/test-thread-pool$(EXESUF): tests/test-thread-pool.o $(test-block-obj-y)
 tests/test-iov$(EXESUF): tests/test-iov.o $(test-util-obj-y)
 tests/test-hbitmap$(EXESUF): tests/test-hbitmap.o $(test-util-obj-y) $(test-crypto-obj-y)
 tests/test-x86-cpuid$(EXESUF): tests/test-x86-cpuid.o
-tests/test-xbzrle$(EXESUF): tests/test-xbzrle.o migration/xbzrle.o migration/page_cache.o $(test-util-obj-y)
+tests/test-xbzrle$(EXESUF): tests/test-xbzrle.o migration/xbzrle.o migration/page_cache.o stubs/pmem.o $(test-util-obj-y)
 tests/test-cutils$(EXESUF): tests/test-cutils.o util/cutils.o $(test-util-obj-y)
 tests/test-int128$(EXESUF): tests/test-int128.o
 tests/rcutorture$(EXESUF): tests/rcutorture.o $(test-util-obj-y)
diff --git a/tests/test-xbzrle.c b/tests/test-xbzrle.c
index f5e08de..9afa0c4 100644
--- a/tests/test-xbzrle.c
+++ b/tests/test-xbzrle.c
@@ -101,7 +101,7 @@ static void test_encode_decode_1_byte(void)
                        PAGE_SIZE);
     g_assert(dlen == (uleb128_encode_small(&buf[0], 4095) + 2));
 
-    rc = xbzrle_decode_buffer(compressed, dlen, buffer, PAGE_SIZE);
+    rc = xbzrle_decode_buffer(compressed, dlen, buffer, PAGE_SIZE, false);
     g_assert(rc == PAGE_SIZE);
     g_assert(memcmp(test, buffer, PAGE_SIZE) == 0);
 
@@ -156,7 +156,7 @@ static void encode_decode_range(void)
     dlen = xbzrle_encode_buffer(test, buffer, PAGE_SIZE, compressed,
                                 PAGE_SIZE);
 
-    rc = xbzrle_decode_buffer(compressed, dlen, test, PAGE_SIZE);
+    rc = xbzrle_decode_buffer(compressed, dlen, test, PAGE_SIZE, false);
     g_assert(rc < PAGE_SIZE);
     g_assert(memcmp(test, buffer, PAGE_SIZE) == 0);
 
-- 
2.7.4