dmaengine: idxd: Flush kernel workqueues on Function Level Reset

When a Function Level Reset (FLR) happens, terminate the pending
descriptors that were issued by in-kernel users and disable the
interrupts associated with those. They will be re-enabled after FLR
finishes.

idxd_wq_flush_desc() is declared on idxd.h because it's going to be
used in by the DMA backend in a future patch.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-4-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: vcgomes

drivers/dma/idxd/device.c

@@ -1339,6 +1339,11 @@ void idxd_wq_free_irq(struct idxd_wq *wq)
 
 	free_irq(ie->vector, ie);
 	idxd_flush_pending_descs(ie);
+
+	/* The interrupt might have been already released by FLR */
+	if (ie->int_handle == INVALID_INT_HANDLE)
+		return;
+
 	if (idxd->request_int_handles)
 		idxd_device_release_int_handle(idxd, ie->int_handle, IDXD_IRQ_MSIX);
 	idxd_device_clear_perm_entry(idxd, ie);
@@ -1347,6 +1352,23 @@ void idxd_wq_free_irq(struct idxd_wq *wq)
 	ie->pasid = IOMMU_PASID_INVALID;
 }
 
+void idxd_wq_flush_descs(struct idxd_wq *wq)
+{
+	struct idxd_irq_entry *ie = &wq->ie;
+	struct idxd_device *idxd = wq->idxd;
+
+	guard(mutex)(&wq->wq_lock);
+
+	if (wq->state != IDXD_WQ_ENABLED || wq->type != IDXD_WQT_KERNEL)
+		return;
+
+	idxd_flush_pending_descs(ie);
+	if (idxd->request_int_handles)
+		idxd_device_release_int_handle(idxd, ie->int_handle, IDXD_IRQ_MSIX);
+	idxd_device_clear_perm_entry(idxd, ie);
+	ie->int_handle = INVALID_INT_HANDLE;
+}
+
 int idxd_wq_request_irq(struct idxd_wq *wq)
 {
 	struct idxd_device *idxd = wq->idxd;

drivers/dma/idxd/idxd.h

@@ -803,6 +803,7 @@ void idxd_wq_quiesce(struct idxd_wq *wq);
 int idxd_wq_init_percpu_ref(struct idxd_wq *wq);
 void idxd_wq_free_irq(struct idxd_wq *wq);
 int idxd_wq_request_irq(struct idxd_wq *wq);
+void idxd_wq_flush_descs(struct idxd_wq *wq);
 
 /* submission */
 int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc);

drivers/dma/idxd/irq.c

@@ -397,6 +397,17 @@ static void idxd_device_flr(struct work_struct *work)
 		dev_err(&idxd->pdev->dev, "FLR failed\n");
 }
 
+static void idxd_wqs_flush_descs(struct idxd_device *idxd)
+{
+	int i;
+
+	for (i = 0; i < idxd->max_wqs; i++) {
+		struct idxd_wq *wq = idxd->wqs[i];
+
+		idxd_wq_flush_descs(wq);
+	}
+}
+
 static irqreturn_t idxd_halt(struct idxd_device *idxd)
 {
 	union gensts_reg gensts;
@@ -415,6 +426,11 @@ static irqreturn_t idxd_halt(struct idxd_device *idxd)
 		} else if (gensts.reset_type == IDXD_DEVICE_RESET_FLR) {
 			idxd->state = IDXD_DEV_HALTED;
 			idxd_mask_error_interrupts(idxd);
+			/* Flush all pending descriptors, and disable
+			 * interrupts, they will be re-enabled when FLR
+			 * concludes.
+			 */
+			idxd_wqs_flush_descs(idxd);
 			dev_dbg(&idxd->pdev->dev,
 				"idxd halted, doing FLR. After FLR, configs are restored\n");
 			INIT_WORK(&idxd->work, idxd_device_flr);