vfio/platform: trigger an interrupt via eventfd

This patch allows to set an eventfd for a platform device's interrupt,
and also to trigger the interrupt eventfd from userspace for testing.
Level sensitive interrupts are marked as maskable and are handled in
a later patch. Edge triggered interrupts are not advertised as maskable
and are implemented here using a simple and efficient IRQ handler.

Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
[Baptiste Reynal: fix masked interrupt initialization]
Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Reviewed-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

2 files changed, 94 insertions, 2 deletions

diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
index df5c91936a68..611ec80db63a 100644
--- a/drivers/vfio/platform/vfio_platform_irq.c
+++ b/drivers/vfio/platform/vfio_platform_irq.c
@@ -39,12 +39,92 @@ static int vfio_platform_set_irq_unmask(struct vfio_platform_device *vdev,
         return -EINVAL;
 }
 
+static irqreturn_t vfio_irq_handler(int irq, void *dev_id)
+{
+        struct vfio_platform_irq *irq_ctx = dev_id;
+
+        eventfd_signal(irq_ctx->trigger, 1);
+
+        return IRQ_HANDLED;
+}
+
+static int vfio_set_trigger(struct vfio_platform_device *vdev, int index,
+                            int fd, irq_handler_t handler)
+{
+        struct vfio_platform_irq *irq = &vdev->irqs[index];
+        struct eventfd_ctx *trigger;
+        int ret;
+
+        if (irq->trigger) {
+                free_irq(irq->hwirq, irq);
+                kfree(irq->name);
+                eventfd_ctx_put(irq->trigger);
+                irq->trigger = NULL;
+        }
+
+        if (fd < 0) /* Disable only */
+                return 0;
+
+        irq->name = kasprintf(GFP_KERNEL, "vfio-irq[%d](%s)",
+                                                irq->hwirq, vdev->name);
+        if (!irq->name)
+                return -ENOMEM;
+
+        trigger = eventfd_ctx_fdget(fd);
+        if (IS_ERR(trigger)) {
+                kfree(irq->name);
+                return PTR_ERR(trigger);
+        }
+
+        irq->trigger = trigger;
+
+        ret = request_irq(irq->hwirq, handler, 0, irq->name, irq);
+        if (ret) {
+                kfree(irq->name);
+                eventfd_ctx_put(trigger);
+                irq->trigger = NULL;
+                return ret;
+        }
+
+        return 0;
+}
+
 static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
                                          unsigned index, unsigned start,
                                          unsigned count, uint32_t flags,
                                          void *data)
 {
-        return -EINVAL;
+        struct vfio_platform_irq *irq = &vdev->irqs[index];
+        irq_handler_t handler;
+
+        if (vdev->irqs[index].flags & VFIO_IRQ_INFO_AUTOMASKED)
+                return -EINVAL; /* not implemented */
+        else
+                handler = vfio_irq_handler;
+
+        if (!count && (flags & VFIO_IRQ_SET_DATA_NONE))
+                return vfio_set_trigger(vdev, index, -1, handler);
+
+        if (start != 0 || count != 1)
+                return -EINVAL;
+
+        if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
+                int32_t fd = *(int32_t *)data;
+
+                return vfio_set_trigger(vdev, index, fd, handler);
+        }
+
+        if (flags & VFIO_IRQ_SET_DATA_NONE) {
+                handler(irq->hwirq, irq);
+
+        } else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
+                uint8_t trigger = *(uint8_t *)data;
+
+                if (trigger)
+                        handler(irq->hwirq, irq);
+        }
+
+        return 0;
 }
 
 int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
@@ -90,7 +170,12 @@ int vfio_platform_irq_init(struct vfio_platform_device *vdev)
                 if (hwirq < 0)
                         goto err;
 
-                vdev->irqs[i].flags = 0;
+                vdev->irqs[i].flags = VFIO_IRQ_INFO_EVENTFD;
+
+                if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK)
+                        vdev->irqs[i].flags |= VFIO_IRQ_INFO_MASKABLE
+                                                | VFIO_IRQ_INFO_AUTOMASKED;
+
                 vdev->irqs[i].count = 1;
                 vdev->irqs[i].hwirq = hwirq;
         }
@@ -105,6 +190,11 @@ err:
 
 void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
 {
+        int i;
+
+        for (i = 0; i < vdev->num_irqs; i++)
+                vfio_set_trigger(vdev, i, -1, NULL);
+
         vdev->num_irqs = 0;
         kfree(vdev->irqs);
 }
diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
index b119a6c5ac23..aa01cc36af53 100644
--- a/drivers/vfio/platform/vfio_platform_private.h
+++ b/drivers/vfio/platform/vfio_platform_private.h
@@ -31,6 +31,8 @@ struct vfio_platform_irq {
         u32                     flags;
         u32                     count;
         int                     hwirq;
+        char                    *name;
+        struct eventfd_ctx      *trigger;
 };
 
 struct vfio_platform_region {