[PATCH v2 01/16] dmaengine: idxd: make misc interrupt one shot

[Fenghua Yu]

From: Dave Jiang <dave.jiang@xxxxxxxxx>

Current code continuously processes the interrupt as long as the hardware
is setting the status bit. There's no reason to do that since the threaded
handler will get called again if another interrupt is asserted.

Also through testing, it has shown that if a misprogrammed (or malicious)
agent can continuously submit descriptors with bad completion record and
causes errors to be reported via the misc interrupt. Continuous processing
by the thread can cause software hang watchdog to kick off since the thread
isn't giving up the CPU.

Reported-by: Sanjay Kumar <sanjay.k.kumar@xxxxxxxxx>
Tested-by: Tony Zhu <tony.zhu@xxxxxxxxx>
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Co-developed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
 drivers/dma/idxd/irq.c | 38 ++++++++++++--------------------------
 1 file changed, 12 insertions(+), 26 deletions(-)

diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
index aa314ebec587..0d639303b515 100644
--- a/drivers/dma/idxd/irq.c
+++ b/drivers/dma/idxd/irq.c
@@ -217,13 +217,22 @@ static void idxd_int_handle_revoke(struct work_struct *work)
 	kfree(revoke);
 }
 
-static int process_misc_interrupts(struct idxd_device *idxd, u32 cause)
+irqreturn_t idxd_misc_thread(int vec, void *data)
 {
+	struct idxd_irq_entry *irq_entry = data;
+	struct idxd_device *idxd = ie_to_idxd(irq_entry);
 	struct device *dev = &idxd->pdev->dev;
 	union gensts_reg gensts;
 	u32 val = 0;
 	int i;
 	bool err = false;
+	u32 cause;
+
+	cause = ioread32(idxd->reg_base + IDXD_INTCAUSE_OFFSET);
+	if (!cause)
+		return IRQ_NONE;
+
+	iowrite32(cause, idxd->reg_base + IDXD_INTCAUSE_OFFSET);
 
 	if (cause & IDXD_INTC_HALT_STATE)
 		goto halt;
@@ -301,7 +310,7 @@ static int process_misc_interrupts(struct idxd_device *idxd, u32 cause)
 			      val);
 
 	if (!err)
-		return 0;
+		goto out;
 
 halt:
 	gensts.bits = ioread32(idxd->reg_base + IDXD_GENSTATS_OFFSET);
@@ -324,33 +333,10 @@ static int process_misc_interrupts(struct idxd_device *idxd, u32 cause)
 				"idxd halted, need %s.\n",
 				gensts.reset_type == IDXD_DEVICE_RESET_FLR ?
 				"FLR" : "system reset");
-			return -ENXIO;
 		}
 	}
 
-	return 0;
-}
-
-irqreturn_t idxd_misc_thread(int vec, void *data)
-{
-	struct idxd_irq_entry *irq_entry = data;
-	struct idxd_device *idxd = ie_to_idxd(irq_entry);
-	int rc;
-	u32 cause;
-
-	cause = ioread32(idxd->reg_base + IDXD_INTCAUSE_OFFSET);
-	if (cause)
-		iowrite32(cause, idxd->reg_base + IDXD_INTCAUSE_OFFSET);
-
-	while (cause) {
-		rc = process_misc_interrupts(idxd, cause);
-		if (rc < 0)
-			break;
-		cause = ioread32(idxd->reg_base + IDXD_INTCAUSE_OFFSET);
-		if (cause)
-			iowrite32(cause, idxd->reg_base + IDXD_INTCAUSE_OFFSET);
-	}
-
+out:
 	return IRQ_HANDLED;
 }
 
-- 
2.37.1