Per sections 3.6.1 (SD Bus Protocol) and 7.3.2 (Responses):

  In the CMD line the Most Significant Bit is transmitted first.

Use the stl_be_p() helper to store the value in big-endian.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Cédric Le Goater <clg@redhat.com>
---
RFC because I'm surprised this has been unnoticed for 17 years
(commit a1bb27b1e9 "initial SD card emulation", April 2007).

Cc: Peter Maydell <peter.maydell@linaro.org>
---
 hw/sd/sd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index 1f3eea6e84..4e09640852 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -1507,7 +1507,7 @@ static sd_rsp_type_t sd_normal_command(SDState *sd, SDRequest req)
             }
 
             sd->state = sd_sendingdata_state;
-            *(uint32_t *) sd->data = sd_wpbits(sd, req.arg);
+            stl_be_p(sd->data, sd_wpbits(sd, req.arg));
             sd->data_start = addr;
             sd->data_offset = 0;
             return sd_r1;
-- 
2.41.0