[Qemu-devel] [RFC PATCH 2/2] Assign a new irq handler while irqfd enabled

[john.liuli]

From: Li Liu <address@hidden>

This irq handler will get the interrupt reason from a
shared memory. And will be assigned only while irqfd
enabled.

Signed-off-by: Li Liu <address@hidden>
---
 drivers/virtio/virtio_mmio.c |   34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 28ddb55..7229605 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -259,7 +259,31 @@ static irqreturn_t vm_interrupt(int irq, void *opaque)
        return ret;
 }
 
+/* Notify all virtqueues on an interrupt. */
+static irqreturn_t vm_interrupt_irqfd(int irq, void *opaque)
+{
+       struct virtio_mmio_device *vm_dev = opaque;
+       struct virtio_mmio_vq_info *info;
+       unsigned long status;
+       unsigned long flags;
+       irqreturn_t ret = IRQ_NONE;
 
+       /* Read the interrupt reason and reset it */
+       status = *vm_dev->isr_mem;
+       *vm_dev->isr_mem = 0x0;
+
+       if (unlikely(status & VIRTIO_MMIO_INT_CONFIG)) {
+               virtio_config_changed(&vm_dev->vdev);
+               ret = IRQ_HANDLED;
+       }
+
+       spin_lock_irqsave(&vm_dev->lock, flags);
+       list_for_each_entry(info, &vm_dev->virtqueues, node)
+               ret |= vring_interrupt(irq, info->vq);
+       spin_unlock_irqrestore(&vm_dev->lock, flags);
+
+       return ret;
+}
 
 static void vm_del_vq(struct virtqueue *vq)
 {
@@ -391,6 +415,7 @@ error_available:
        return ERR_PTR(err);
 }
 
+#define VIRTIO_MMIO_F_IRQFD        (1 << 7)
 static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
                       struct virtqueue *vqs[],
                       vq_callback_t *callbacks[],
@@ -400,8 +425,13 @@ static int vm_find_vqs(struct virtio_device *vdev, 
unsigned nvqs,
        unsigned int irq = platform_get_irq(vm_dev->pdev, 0);
        int i, err;
 
-       err = request_irq(irq, vm_interrupt, IRQF_SHARED,
-                       dev_name(&vdev->dev), vm_dev);
+       if (*vm_dev->isr_mem & VIRTIO_MMIO_F_IRQFD) {
+               err = request_irq(irq, vm_interrupt_irqfd, IRQF_SHARED,
+                                 dev_name(&vdev->dev), vm_dev);
+       } else {
+               err = request_irq(irq, vm_interrupt, IRQF_SHARED,
+                                 dev_name(&vdev->dev), vm_dev);
+       }
        if (err)
                return err;
 
-- 
1.7.9.5