[PATCH 6.12 104/242] accel/qaic: Handle DBC deactivation if the owner went away

Greg Kroah-Hartman
2026-04-08T18:45:37Z

From: Youssef Samir <youssef.abdulrahman@oss.qualcomm.com>

[ Upstream commit 2feec5ae5df785658924ab6bd91280dc3926507c ]

When a DBC is released, the device sends a QAIC_TRANS_DEACTIVATE_FROM_DEV
transaction to the host over the QAIC_CONTROL MHI channel. QAIC handles
this by calling decode_deactivate() to release the resources allocated for
that DBC. Since that handling is done in the qaic_manage_ioctl() context,
if the user goes away before receiving and handling the deactivation, the
host will be out-of-sync with the DBCs available for use, and the DBC
resources will not be freed unless the device is removed. If another user
loads and requests to activate a network, then the device assigns the same
DBC to that network, QAIC will "indefinitely" wait for dbc->in_use = false,
leading the user process to hang.

As a solution to this, handle QAIC_TRANS_DEACTIVATE_FROM_DEV transactions
that are received after the user has gone away.

Fixes: 129776ac2e38 ("accel/qaic: Add control path")
Signed-off-by: Youssef Samir <youssef.abdulrahman@oss.qualcomm.com>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Reviewed-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Signed-off-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Link: https://patch.msgid.link/20260205123415.3870898-1-youssef.abdulrahman@oss.qualcomm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/accel/qaic/qaic_control.c | 47 +++++++++++++++++++++++++++++--
1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/drivers/accel/qaic/qaic_control.c b/drivers/accel/qaic/qaic_control.c
index b86a8e48e731b..8eae30fe14f98 100644
--- a/drivers/accel/qaic/qaic_control.c
+++ b/drivers/accel/qaic/qaic_control.c
@@ -910,7 +910,7 @@ static int decode_deactivate(struct qaic_device *qdev, void *trans, u32 *msg_len
*/
return -ENODEV;

- if (status) {
+ if (usr && status) {
/*
* Releasing resources failed on the device side, which puts
* us in a bind since they may still be in use, so enable the
@@ -1105,6 +1105,9 @@ static void *msg_xfer(struct qaic_device *qdev, struct wrapper_list *wrappers, u
mutex_lock(&qdev->cntl_mutex);
if (!list_empty(&elem.list))
list_del(&elem.list);
+ /* resp_worker() processed the response but the wait was interrupted */
+ else if (ret == -ERESTARTSYS)
+ ret = 0;
if (!ret && !elem.buf)
ret = -ETIMEDOUT;
else if (ret > 0 && !elem.buf)
@@ -1415,9 +1418,49 @@ static void resp_worker(struct work_struct *work)
}
mutex_unlock(&qdev->cntl_mutex);

- if (!found)
+ if (!found) {
+ /*
+ * The user might have gone away at this point without waiting
+ * for QAIC_TRANS_DEACTIVATE_FROM_DEV transaction coming from
+ * the device. If this is not handled correctly, the host will
+ * not know that the DBC[n] has been freed on the device.
+ * Due to this failure in synchronization between the device and
+ * the host, if another user requests to activate a network, and
+ * the device assigns DBC[n] again, save_dbc_buf() will hang,
+ * waiting for dbc[n]->in_use to be set to false, which will not
+ * happen unless the qaic_dev_reset_clean_local_state() gets
+ * called by resetting the device (or re-inserting the module).
+ *
+ * As a solution, we look for QAIC_TRANS_DEACTIVATE_FROM_DEV
+ * transactions in the message before disposing of it, then
+ * handle releasing the DBC resources.
+ *
+ * Since the user has gone away, if the device could not
+ * deactivate the network (status != 0), there is no way to
+ * enable and reassign the DBC to the user. We can put trust in
+ * the device that it will release all the active DBCs in
+ * response to the QAIC_TRANS_TERMINATE_TO_DEV transaction,
+ * otherwise, the user can issue an soc_reset to the device.
+ */
+ u32 msg_count = le32_to_cpu(msg->hdr.count);
+ u32 msg_len = le32_to_cpu(msg->hdr.len);
+ u32 len = 0;
+ int j;
+
+ for (j = 0; j < msg_count && len < msg_len; ++j) {
+ struct wire_trans_hdr *trans_hdr;
+
+ trans_hdr = (struct wire_trans_hdr *)(msg->data + len);
+ if (le32_to_cpu(trans_hdr->type) == QAIC_TRANS_DEACTIVATE_FROM_DEV) {
+ if (decode_deactivate(qdev, trans_hdr, &len, NULL))
+ len += le32_to_cpu(trans_hdr->len);
+ } else {
+ len += le32_to_cpu(trans_hdr->len);
+ }
+ }
/* request must have timed out, drop packet */
kfree(msg);
+ }

kfree(resp);
}
--
2.53.0