[PATCH kvmtool 3/9] vfio: Support edge-triggered wired IRQs

[Mostafa Saleh <smostafa@google.com>]

PCI INTx is are level-triggered and automasked, but platform
device interrupts can also be edge-triggered.

Pass an automasked boolean to vfio_irq_enable() and only create and
register unmask_fd when the interrupt is automasked.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 include/kvm/vfio.h |  2 +-
 vfio/core.c        | 51 ++++++++++++++++++++++++++--------------------
 vfio/pci.c         |  3 ++-
 3 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/include/kvm/vfio.h b/include/kvm/vfio.h
index 9a5783e..0b2b105 100644
--- a/include/kvm/vfio.h
+++ b/include/kvm/vfio.h
@@ -141,7 +141,7 @@ int vfio_map_region(struct kvm *kvm, struct vfio_device *vdev,
 		    struct vfio_region *region);
 void vfio_unmap_region(struct kvm *kvm, struct vfio_region *region);
 int vfio_irq_enable(struct kvm *kvm, struct vfio_device *vdev,
-		    unsigned int index, struct vfio_irq *irq);
+		    unsigned int index, bool automasked, struct vfio_irq *irq);
 void vfio_irq_disable(struct kvm *kvm, struct vfio_device *vdev,
 		      unsigned int index, struct vfio_irq *irq);
 int vfio_pci_setup_device(struct kvm *kvm, struct vfio_device *device);
diff --git a/vfio/core.c b/vfio/core.c
index 24d3f2d..aa124d2 100644
--- a/vfio/core.c
+++ b/vfio/core.c
@@ -301,15 +301,16 @@ void vfio_irq_disable(struct kvm *kvm, struct vfio_device *vdev,
 	irq__del_irqfd(kvm, gsi, irq->trigger_fd);
 
 	close(irq->trigger_fd);
-	close(irq->unmask_fd);
+	if (irq->unmask_fd >= 0)
+		close(irq->unmask_fd);
 	irq->trigger_fd = -1;
 }
 
 int vfio_irq_enable(struct kvm *kvm, struct vfio_device *vdev,
-		    unsigned int index, struct vfio_irq *irq)
+		    unsigned int index, bool automasked, struct vfio_irq *irq)
 {
 	int ret;
-	int trigger_fd, unmask_fd;
+	int trigger_fd, unmask_fd = -1;
 	union vfio_irq_eventfd	trigger;
 	union vfio_irq_eventfd	unmask;
 	int gsi = irq->gsi;
@@ -318,7 +319,7 @@ int vfio_irq_enable(struct kvm *kvm, struct vfio_device *vdev,
 		return 0;
 
 	/*
-	 * PCI IRQ is level-triggered, so we use two eventfds. trigger_fd
+	 * Level-triggered IRQ is automasked, so we use two eventfds. trigger_fd
 	 * signals an interrupt from host to guest, and unmask_fd signals the
 	 * deassertion of the line from guest to host.
 	 */
@@ -328,11 +329,13 @@ int vfio_irq_enable(struct kvm *kvm, struct vfio_device *vdev,
 		return trigger_fd;
 	}
 
-	unmask_fd = eventfd(0, 0);
-	if (unmask_fd < 0) {
-		vfio_dev_err(vdev, "failed to create unmask eventfd");
-		close(trigger_fd);
-		return unmask_fd;
+	if (automasked) {
+		unmask_fd = eventfd(0, 0);
+		if (unmask_fd < 0) {
+			vfio_dev_err(vdev, "failed to create unmask eventfd");
+			close(trigger_fd);
+			return unmask_fd;
+		}
 	}
 
 	ret = irq__add_irqfd(kvm, gsi, trigger_fd, unmask_fd);
@@ -354,19 +357,22 @@ int vfio_irq_enable(struct kvm *kvm, struct vfio_device *vdev,
 		goto err_delete_line;
 	}
 
-	unmask.irq = (struct vfio_irq_set) {
-		.argsz	= sizeof(unmask),
-		.flags	= VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_UNMASK,
-		.index	= index,
-		.start	= 0,
-		.count	= 1,
-	};
-	set_vfio_irq_eventd_payload(&unmask, unmask_fd);
+	if (unmask_fd >= 0) {
+		unmask.irq = (struct vfio_irq_set) {
+			.argsz	= sizeof(unmask),
+			.flags	= VFIO_IRQ_SET_DATA_EVENTFD |
+				  VFIO_IRQ_SET_ACTION_UNMASK,
+			.index	= index,
+			.start	= 0,
+			.count	= 1,
+		};
+		set_vfio_irq_eventd_payload(&unmask, unmask_fd);
 
-	ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &unmask);
-	if (ret < 0) {
-		vfio_dev_err(vdev, "failed to setup unmask IRQ");
-		goto err_remove_event;
+		ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &unmask);
+		if (ret < 0) {
+			vfio_dev_err(vdev, "failed to setup unmask IRQ");
+			goto err_remove_event;
+		}
 	}
 
 	irq->trigger_fd = trigger_fd;
@@ -385,7 +391,8 @@ err_delete_line:
 
 err_close:
 	close(trigger_fd);
-	close(unmask_fd);
+	if (unmask_fd >= 0)
+		close(unmask_fd);
 	return ret;
 }
 
diff --git a/vfio/pci.c b/vfio/pci.c
index fb98435..9bf2f9e 100644
--- a/vfio/pci.c
+++ b/vfio/pci.c
@@ -1216,7 +1216,8 @@ static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev)
 {
 	struct vfio_pci_device *pdev = &vdev->pci;
 
-	return vfio_irq_enable(kvm, vdev, VFIO_PCI_INTX_IRQ_INDEX, &pdev->intx);
+	return vfio_irq_enable(kvm, vdev, VFIO_PCI_INTX_IRQ_INDEX, true,
+			       &pdev->intx);
 }
 
 static int vfio_pci_init_intx(struct kvm *kvm, struct vfio_device *vdev)
-- 
2.56.0.307.g5fe7bd680c-goog