dmaengine: idxd: remove MSIX masking for interrupt handlers

Commit Message

Dave Jiang April 20, 2021, 7 p.m. UTC

Remove interrupt masking and just let the hard irq handler keep
firing for new events. This is less of a performance impact vs
the MMIO readback inside the pci_msi_{mask,unmas}_irq(). Especially
with a loaded system those flushes can be stuck behind large amounts
of MMIO writes to flush. When guest kernel is running on top of VFIO
mdev, mask/unmask causes a vmexit each time and is not desirable.

Suggested-by: Dan Williams <[e-mail]>
Signed-off-by: Dave Jiang <[e-mail]>
Reviewed-by: Dan Williams <[e-mail]>
---
 drivers/dma/idxd/idxd.h |    1 -
 drivers/dma/idxd/init.c |    4 ++--
 drivers/dma/idxd/irq.c  |   12 ------------
 3 files changed, 2 insertions(+), 15 deletions(-)

Comments

Vinod Koul April 23, 2021, 5:39 p.m. UTC | #1

On 20-04-21, 12:00, Dave Jiang wrote:
> Remove interrupt masking and just let the hard irq handler keep
> firing for new events. This is less of a performance impact vs
> the MMIO readback inside the pci_msi_{mask,unmas}_irq(). Especially
> with a loaded system those flushes can be stuck behind large amounts
> of MMIO writes to flush. When guest kernel is running on top of VFIO
> mdev, mask/unmask causes a vmexit each time and is not desirable.

Applied, thanks

Patch

diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
index d7185c6bfade..7237f3e15a5e 100644
--- a/drivers/dma/idxd/idxd.h
+++ b/drivers/dma/idxd/idxd.h
@@ -376,7 +376,6 @@  void idxd_wqs_quiesce(struct idxd_device *idxd);
 /* device interrupt control */
 void idxd_msix_perm_setup(struct idxd_device *idxd);
 void idxd_msix_perm_clear(struct idxd_device *idxd);
-irqreturn_t idxd_irq_handler(int vec, void *data);
 irqreturn_t idxd_misc_thread(int vec, void *data);
 irqreturn_t idxd_wq_thread(int irq, void *data);
 void idxd_mask_error_interrupts(struct idxd_device *idxd);
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index e6bfd55e421b..36b33eef5aa2 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -102,7 +102,7 @@  static int idxd_setup_interrupts(struct idxd_device *idxd)
 	}
 
 	irq_entry = &idxd->irq_entries[0];
-	rc = request_threaded_irq(irq_entry->vector, idxd_irq_handler, idxd_misc_thread,
+	rc = request_threaded_irq(irq_entry->vector, NULL, idxd_misc_thread,
 				  0, "idxd-misc", irq_entry);
 	if (rc < 0) {
 		dev_err(dev, "Failed to allocate misc interrupt.\n");
@@ -119,7 +119,7 @@  static int idxd_setup_interrupts(struct idxd_device *idxd)
 
 		init_llist_head(&idxd->irq_entries[i].pending_llist);
 		INIT_LIST_HEAD(&idxd->irq_entries[i].work_list);
-		rc = request_threaded_irq(irq_entry->vector, idxd_irq_handler,
+		rc = request_threaded_irq(irq_entry->vector, NULL,
 					  idxd_wq_thread, 0, "idxd-portal", irq_entry);
 		if (rc < 0) {
 			dev_err(dev, "Failed to allocate irq %d.\n", irq_entry->vector);
diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
index 43eea5c9cbd4..afee571e0194 100644
--- a/drivers/dma/idxd/irq.c
+++ b/drivers/dma/idxd/irq.c
@@ -102,15 +102,6 @@  static int idxd_device_schedule_fault_process(struct idxd_device *idxd,
 	return 0;
 }
 
-irqreturn_t idxd_irq_handler(int vec, void *data)
-{
-	struct idxd_irq_entry *irq_entry = data;
-	struct idxd_device *idxd = irq_entry->idxd;
-
-	idxd_mask_msix_vector(idxd, irq_entry->id);
-	return IRQ_WAKE_THREAD;
-}
-
 static int process_misc_interrupts(struct idxd_device *idxd, u32 cause)
 {
 	struct device *dev = &idxd->pdev->dev;
@@ -237,7 +228,6 @@  irqreturn_t idxd_misc_thread(int vec, void *data)
 			iowrite32(cause, idxd->reg_base + IDXD_INTCAUSE_OFFSET);
 	}
 
-	idxd_unmask_msix_vector(idxd, irq_entry->id);
 	return IRQ_HANDLED;
 }
 
@@ -394,8 +384,6 @@  irqreturn_t idxd_wq_thread(int irq, void *data)
 	int processed;
 
 	processed = idxd_desc_process(irq_entry);
-	idxd_unmask_msix_vector(irq_entry->idxd, irq_entry->id);
-
 	if (processed == 0)
 		return IRQ_NONE;