scsi-bus: fix transfer length and direction for VERIFY command

The amount of bytes to transfer depends on the BYTCHK field.
If any data is transferred, it is sent to the device.

Cc: qemu-stable@nongnu.org
Tested-by: NHervé Poussineau <hpoussin@reactos.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi/scsi-bus.c

@@ -886,7 +886,6 @@ static int scsi_req_length(SCSICommand *cmd, SCSIDevice *dev, uint8_t *buf)
     case RELEASE:
     case ERASE:
     case ALLOW_MEDIUM_REMOVAL:
-    case VERIFY_10:
     case SEEK_10:
     case SYNCHRONIZE_CACHE:
     case SYNCHRONIZE_CACHE_16:
@@ -903,6 +902,16 @@ static int scsi_req_length(SCSICommand *cmd, SCSIDevice *dev, uint8_t *buf)
     case ALLOW_OVERWRITE:
         cmd->xfer = 0;
         break;
+    case VERIFY_10:
+    case VERIFY_12:
+    case VERIFY_16:
+        if ((buf[1] & 2) == 0) {
+            cmd->xfer = 0;
+        } else if ((buf[1] & 4) == 1) {
+            cmd->xfer = 1;
+        }
+        cmd->xfer *= dev->blocksize;
+        break;
     case MODE_SENSE:
         break;
     case WRITE_SAME_10:
@@ -1100,6 +1109,9 @@ static void scsi_cmd_xfer_mode(SCSICommand *cmd)
     case WRITE_VERIFY_12:
     case WRITE_16:
     case WRITE_VERIFY_16:
+    case VERIFY_10:
+    case VERIFY_12:
+    case VERIFY_16:
     case COPY:
     case COPY_VERIFY:
     case COMPARE: