Index: block-raw-posix.c
===================================================================
--- block-raw-posix.c.orig
+++ block-raw-posix.c
@@ -77,6 +77,7 @@
 typedef struct BDRVRawState {
     int fd;
     int type;
+    int flags;
     unsigned int lseek_err_cnt;
 #if defined(__linux__)
     /* linux floppy specific */
@@ -95,6 +96,7 @@ static int raw_open(BlockDriverState *bs
     BDRVRawState *s = bs->opaque;
     int fd, open_flags, ret;
 
+    s->flags = flags;
     s->lseek_err_cnt = 0;
 
     open_flags = O_BINARY;
@@ -141,7 +143,14 @@ static int raw_open(BlockDriverState *bs
 #endif
 */
 
-static int raw_pread(BlockDriverState *bs, int64_t offset,
+/* 
+ * offset and count are in bytes, but must be multiples of 512 for files 
+ * opened with O_DIRECT. buf must be aligned to 512 bytes then.
+ *
+ * This function may be called without alignment if the caller ensures
+ * that O_DIRECT is not in effect.
+ */
+static int raw_pread_aligned(BlockDriverState *bs, int64_t offset,
                      uint8_t *buf, int count)
 {
     BDRVRawState *s = bs->opaque;
@@ -194,7 +203,14 @@ label__raw_read__success:
     return ret;
 }
 
-static int raw_pwrite(BlockDriverState *bs, int64_t offset,
+/* 
+ * offset and count are in bytes, but must be multiples of 512 for files 
+ * opened with O_DIRECT. buf must be aligned to 512 bytes then.
+ *
+ * This function may be called without alignment if the caller ensures
+ * that O_DIRECT is not in effect.
+ */
+static int raw_pwrite_aligned(BlockDriverState *bs, int64_t offset,
                       const uint8_t *buf, int count)
 {
     BDRVRawState *s = bs->opaque;
@@ -230,6 +246,69 @@ label__raw_write__success:
     return ret;
 }
 
+
+#ifdef O_DIRECT
+/* 
+ * offset and count are in bytes and possibly not aligned. For files opened 
+ * with O_DIRECT, necessary alignments are ensured before calling 
+ * raw_pread_aligned to do the actual read.
+ */
+static int raw_pread(BlockDriverState *bs, int64_t offset,
+                     uint8_t *buf, int count)
+{
+    BDRVRawState *s = bs->opaque;
+
+    if (unlikely((s->flags & BDRV_O_DIRECT) &&
+            (offset % 512 != 0 || (uintptr_t) buf % 512))) {
+
+        int flags, ret;
+
+        // Temporarily disable O_DIRECT for unaligned access
+        flags = fcntl(s->fd, F_GETFL);
+        fcntl(s->fd, F_SETFL, flags & ~O_DIRECT);
+        ret = raw_pread_aligned(bs, offset, buf, count);
+        fcntl(s->fd, F_SETFL, flags);
+
+        return ret;
+
+    } else {
+        return raw_pread_aligned(bs, offset, buf, count);
+    }
+}
+
+/* 
+ * offset and count are in bytes and possibly not aligned. For files opened 
+ * with O_DIRECT, necessary alignments are ensured before calling 
+ * raw_pwrite_aligned to do the actual write.
+ */
+static int raw_pwrite(BlockDriverState *bs, int64_t offset,
+                      const uint8_t *buf, int count)
+{
+    BDRVRawState *s = bs->opaque;
+
+    if (unlikely((s->flags & BDRV_O_DIRECT) &&
+            (offset % 512 != 0 || (uintptr_t) buf % 512))) {
+
+        int flags, ret;
+
+        // Temporarily disable O_DIRECT for unaligned access
+        flags = fcntl(s->fd, F_GETFL);
+        fcntl(s->fd, F_SETFL, flags & ~O_DIRECT);
+        ret = raw_pwrite_aligned(bs, offset, buf, count);
+        fcntl(s->fd, F_SETFL, flags);
+
+        return ret;
+    } else {
+        return raw_pwrite_aligned(bs, offset, buf, count);
+    }
+}
+
+#else
+#define raw_pread raw_pread_aligned
+#define raw_pwrite raw_pwrite_aligned
+#endif
+
+
 /***********************************************************/
 /* Unix AIO using POSIX AIO */