[PATCH v1] vdpa/snet: Don't discard the DPU error in snet_send_ctrl_msg()

[Yuho Choi <oss.patchbox@gmail.com>]

snet_send_ctrl_msg() reads the error code the DPU reports when it ACKs
a control message, but then overwrites it with the return value of
snet_wait_for_dpu_completion(). As a result, a DESTROY, SUSPEND or
RESUME that the DPU rejects is reported to the caller as a success as
long as the DPU clears the opcode register in time.

For SUSPEND this means vhost-vdpa marks the device as suspended and
lets userspace reprogram the vrings while the DPU is still running
them; for DESTROY, snet_reset_dev() never even sees that the device
failed to stop.

Return the error from the saved ACK value once the completion wait
itself has succeeded.

Fixes: 3f3a1675b731 ("vdpa/snet: support getting and setting VQ state")
Cc: stable@vger.kernel.org
Signed-off-by: Yuho Choi <oss.patchbox@gmail.com>
---
Compile-tested only (x86_64 defconfig + SNET_VDPA, W=1, sparse).

 drivers/vdpa/solidrun/snet_ctrl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/solidrun/snet_ctrl.c b/drivers/vdpa/solidrun/snet_ctrl.c
index e284c3a06717..09afa0487fd6 100644
--- a/drivers/vdpa/solidrun/snet_ctrl.c
+++ b/drivers/vdpa/solidrun/snet_ctrl.c
@@ -291,7 +291,6 @@ static int snet_send_ctrl_msg(struct snet *snet, u16 opcode, u16 vq_idx)
 
 	/* Check for errors */
 	val = snet_read_ctrl(regs);
-	ret = SNET_VAL_TO_ERR(val);
 
 	/* Clear the chunk ready bit */
 	val &= ~SNET_CTRL_CHUNK_RDY_MASK;
@@ -301,6 +300,8 @@ static int snet_send_ctrl_msg(struct snet *snet, u16 opcode, u16 vq_idx)
 	if (ret)
 		SNET_WARN(pdev, "Timeout waiting for DPU to complete a control command, err %d\n",
 			  ret);
+	else
+		ret = SNET_VAL_TO_ERR(val);
 
 exit:
 	mutex_unlock(&snet->ctrl_lock);

base-commit: 7704c4c5bb127673b4f0ead839919db573559e38
-- 
2.43.0