[PATCHv2 2/2] nvme/pci: Mask device interrupts for threaded handlers

[Keith Busch <kbusch@kernel.org>]

Local interrupts are reenabled when the nvme irq thread is woken, so
subsequent MSI or a level triggered interrupts may restart the nvme irq
check while the thread handler is running. This unnecessarily spends CPU
cycles and potentially triggers spurious interrupt detection, disabling
our nvme irq.

Prevent the controller from sending future messages. For legacy and MSI,
use the nvme interrupt mask/clear registers. For MSIx, use the quick
control mask function.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/nvme/host/pci.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0590640ba62c..4022a872d29c 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -13,8 +13,10 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/irq.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/msi.h>
 #include <linux/mutex.h>
 #include <linux/once.h>
 #include <linux/pci.h>
@@ -1036,12 +1038,29 @@ static irqreturn_t nvme_irq(int irq, void *data)
 	return ret;
 }
 
+static irqreturn_t nvme_irq_thread(int irq, void *data)
+{
+	struct nvme_queue *nvmeq = data;
+
+	nvme_irq(irq, data);
+	if (to_pci_dev(nvmeq->dev->dev)->msix_enabled)
+		__pci_msix_desc_mask_irq(irq_get_msi_desc(irq), 0);
+	else
+		writel(1 << nvmeq->cq_vector, nvmeq->dev->bar + NVME_REG_INTMC);
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t nvme_irq_check(int irq, void *data)
 {
 	struct nvme_queue *nvmeq = data;
-	if (nvme_cqe_pending(nvmeq))
-		return IRQ_WAKE_THREAD;
-	return IRQ_NONE;
+
+	if (!nvme_cqe_pending(nvmeq))
+		return IRQ_NONE;
+	if (to_pci_dev(nvmeq->dev->dev)->msix_enabled)
+		__pci_msix_desc_mask_irq(irq_get_msi_desc(irq), 1);
+	else
+		writel(1 << nvmeq->cq_vector, nvmeq->dev->bar + NVME_REG_INTMS);
+	return IRQ_WAKE_THREAD;
 }
 
 /*
@@ -1499,7 +1518,8 @@ static int queue_request_irq(struct nvme_queue *nvmeq)
 
 	if (use_threaded_interrupts) {
 		return pci_request_irq(pdev, nvmeq->cq_vector, nvme_irq_check,
-				nvme_irq, nvmeq, "nvme%dq%d", nr, nvmeq->qid);
+				nvme_irq_thread, nvmeq, "nvme%dq%d", nr,
+				nvmeq->qid);
 	} else {
 		return pci_request_irq(pdev, nvmeq->cq_vector, nvme_irq,
 				NULL, nvmeq, "nvme%dq%d", nr, nvmeq->qid);
-- 
2.21.0


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