Re: [PATCH 3/5] VFIO: Support threaded interrupt handling on VFIO

Alex Williamson
2015-12-16T19:49:11Z

On Thu, 2015-12-03 at 10:22 -0800, Yunhong Jiang wrote:
> For VFIO device with MSI interrupt type, it's possible to handle the
> interrupt on hard interrupt context without invoking the interrupt
> thread. Handling the interrupt on hard interrupt context reduce the
> interrupt latency.
>
> Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c | 39 ++++++++++++++++++++++++++++++++++-----
>  1 file changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 3b3ba15558b7..108d335c5656 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -236,12 +236,35 @@ static void vfio_intx_disable(struct vfio_pci_device *vdev)
>   kfree(vdev->ctx);
>  }
>
> +static irqreturn_t vfio_msihandler(int irq, void *arg)
> +{
> + struct vfio_pci_irq_ctx *ctx = arg;
> + struct irq_bypass_producer *producer = &ctx->producer;
> + struct irq_bypass_consumer *consumer;
> + int ret = IRQ_HANDLED, idx;
> +
> + idx = srcu_read_lock(&producer->srcu);
> +
> + list_for_each_entry_rcu(consumer, &producer->consumers, sibling) {
> + /*
> +  * Invoke the thread handler if any consumer would block, but
> +  * finish all consumes.
> +  */
> + if (consumer->handle_irq(consumer->irq_context) == -EWOULDBLOCK)
> + ret = IRQ_WAKE_THREAD;
> + continue;
> + }
> +
> + srcu_read_unlock(&producer->srcu, idx);

There should be an irq bypass manager interface to abstract this.