Re: [PATCH v9 12/19] vfio/platform: trigger an interrupt via eventfd

[Eric Auger <eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On 10/31/2014 08:36 PM, Alex Williamson wrote:
> On Mon, 2014-10-27 at 19:07 +0100, Antonios Motakis wrote:
>> This patch allows to set an eventfd for a patform device's interrupt,
platform device (typo)
>> 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-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>
>> ---
>>  drivers/vfio/platform/vfio_platform_irq.c     | 93 ++++++++++++++++++++++++++-
>>  drivers/vfio/platform/vfio_platform_private.h |  2 +
>>  2 files changed, 93 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
>> index 007b386..2ac8ed7 100644
>> --- a/drivers/vfio/platform/vfio_platform_irq.c
>> +++ b/drivers/vfio/platform/vfio_platform_irq.c
>> @@ -45,11 +45,91 @@ 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;
you may simply return ret here?
>> +}
>> +
>>  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_MASKABLE)
>> +		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,
>> @@ -95,7 +175,11 @@ 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;
> 
> This is a bit confusing because edge interrupts can support masking, but
> they don't require it.  Level interrupts really must support masking
> because we need to mask them on the host and therefore the user needs to
> be able to unmask them (ignoring the irq prioritization thing you guys
> can do on arm).  So this works, but I would really have expected
> VFIO_IRQ_INFO_AUTOMASKED here and in the above function.

Shouldn't we have AUTOMASKED for level sensitive and MASKABLE for both
level & edge?

For forwarded IRQ, may I enrich the external API with a new function
enabling to turn the automasked flag off? Would that make sense?

Thanks

Eric
> 
>> +
>>  		vdev->irqs[i].count = 1;
>>  		vdev->irqs[i].hwirq = hwirq;
>>  	}
>> @@ -110,6 +194,11 @@ 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 ffa2459..a3f2411 100644
>> --- a/drivers/vfio/platform/vfio_platform_private.h
>> +++ b/drivers/vfio/platform/vfio_platform_private.h
>> @@ -28,6 +28,8 @@ struct vfio_platform_irq {
>>  	u32			flags;
>>  	u32			count;
>>  	int			hwirq;
>> +	char			*name;
>> +	struct eventfd_ctx	*trigger;
>>  };
>>  
>>  struct vfio_platform_region {
> 
> 
>