Re: [Qemu-devel] [PATCH RFC v2 11/15] vfio: ccw: introduce ioctls to get/set VFIO_CCW_IO_IRQ

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 12 Jan 2017 08:19:43 +0100
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> Realize VFIO_DEVICE_GET_IRQ_INFO ioctl to retrieve
> VFIO_CCW_IO_IRQ information.
> 
> Realize VFIO_DEVICE_SET_IRQS ioctl to set an eventfd fd for
> VFIO_CCW_IO_IRQ. Once a write operation to the ccw_io_region
> was performed, trigger a signal on this fd.
> 
> Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
> ---
>  drivers/s390/cio/vfio_ccw_ops.c     | 125 +++++++++++++++++++++++++++++++++++-
>  drivers/s390/cio/vfio_ccw_private.h |   4 ++
>  include/uapi/linux/vfio.h           |  10 ++-
>  3 files changed, 136 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
> index b702735..3c47eb6 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -203,6 +203,9 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
>  	if (region->ret_code != 0)
>  		return region->ret_code;
>  
> +	if (private->io_trigger)
> +		eventfd_signal(private->io_trigger, 1);
> +
>  	return count;
>  }
>  
> @@ -211,7 +214,7 @@ static int vfio_ccw_mdev_get_device_info(struct mdev_device *mdev,
>  {
>  	info->flags = VFIO_DEVICE_FLAGS_CCW | VFIO_DEVICE_FLAGS_RESET;
>  	info->num_regions = VFIO_CCW_NUM_REGIONS;
> -	info->num_irqs = 0;
> +	info->num_irqs = VFIO_CCW_NUM_IRQS;
>  
>  	return 0;
>  }
> @@ -233,6 +236,84 @@ static int vfio_ccw_mdev_get_region_info(struct mdev_device *mdev,
>  	}
>  }
>  
> +int vfio_ccw_mdev_get_irq_info(struct mdev_device *mdev,
> +			       struct vfio_irq_info *info)
> +{
> +	if (info->index != VFIO_CCW_IO_IRQ_INDEX)
> +		return -EINVAL;
> +
> +	info->count = VFIO_CCW_NUM_IRQS;
> +	info->flags = VFIO_IRQ_INFO_EVENTFD | VFIO_IRQ_INFO_NORESIZE;


VFIO_CCW_NUM_IRQS is not being used correctly here, info->count is the
number of interrupts within this index, VFIO_CCW_NUM_IRQS is the number
of indexes.  This is meant to handle things like PCI where we have 3
different interrupts types (INTx, MSI, MSI-X) and some of those (MSI/X)
support multiple vectors.  In this case I think you want info->count =
1 and you don't need the NORESIZE flag since that only makes sense for
describing indexes where a subset of the available vectors may be
enabled.  So info->count comes out to the same thing, but should not
use the same macro to get there.

> +
> +	return 0;
> +}
> +
> +static int vfio_ccw_mdev_set_irqs(struct mdev_device *mdev,
> +				  uint32_t flags,
> +				  void __user *data)
> +{
> +	struct vfio_ccw_private *private;
> +	struct eventfd_ctx **ctx;
> +
> +	if (!(flags & VFIO_IRQ_SET_ACTION_TRIGGER))
> +		return -EINVAL;
> +
> +	private = dev_get_drvdata(mdev->dev.parent);
> +	if (!private)
> +		return -ENODEV;
> +
> +	ctx = &private->io_trigger;
> +
> +	switch (flags & VFIO_IRQ_SET_DATA_TYPE_MASK) {
> +	case VFIO_IRQ_SET_DATA_NONE:
> +	{
> +		if (*ctx)
> +			eventfd_signal(*ctx, 1);
> +		return 0;
> +	}
> +	case VFIO_IRQ_SET_DATA_BOOL:
> +	{
> +		uint8_t trigger;
> +
> +		if (get_user(trigger, (uint8_t __user *)data))
> +			return -EFAULT;
> +
> +		if (trigger && *ctx)
> +			eventfd_signal(*ctx, 1);
> +		return 0;
> +	}
> +	case VFIO_IRQ_SET_DATA_EVENTFD:
> +	{
> +		int32_t fd;
> +
> +		if (get_user(fd, (int32_t __user *)data))
> +			return -EFAULT;
> +
> +		if (fd == -1) {
> +			if (*ctx)
> +				eventfd_ctx_put(*ctx);
> +			*ctx = NULL;
> +		} else if (fd >= 0) {
> +			struct eventfd_ctx *efdctx;
> +
> +			efdctx = eventfd_ctx_fdget(fd);
> +			if (IS_ERR(efdctx))
> +				return PTR_ERR(efdctx);
> +
> +			if (*ctx)
> +				eventfd_ctx_put(*ctx);
> +
> +			*ctx = efdctx;
> +		} else
> +			return -EINVAL;
> +
> +		return 0;
> +	}
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device *mdev,
>  				   unsigned int cmd,
>  				   unsigned long arg)
> @@ -281,6 +362,48 @@ static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device *mdev,
>  
>  		return copy_to_user((void __user *)arg, &info, minsz);
>  	}
> +	case VFIO_DEVICE_GET_IRQ_INFO:
> +	{
> +		struct vfio_irq_info info;
> +
> +		minsz = offsetofend(struct vfio_irq_info, count);
> +
> +		if (copy_from_user(&info, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (info.argsz < minsz || info.index >= VFIO_CCW_NUM_IRQS)
> +			return -EINVAL;
> +
> +		ret = vfio_ccw_mdev_get_irq_info(mdev, &info);
> +		if (ret)
> +			return ret;
> +
> +		if (info.count == -1)
> +			return -EINVAL;
> +
> +		return copy_to_user((void __user *)arg, &info, minsz);
> +	}
> +	case VFIO_DEVICE_SET_IRQS:
> +	{
> +		struct vfio_irq_set hdr;
> +		size_t data_size;
> +		void __user *data;
> +
> +		minsz = offsetofend(struct vfio_irq_set, count);
> +
> +		if (copy_from_user(&hdr, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		ret = vfio_set_irqs_validate_and_prepare(&hdr,
> +							 VFIO_CCW_NUM_IRQS,
> +							 VFIO_CCW_NUM_IRQS,
> +							 &data_size);


This is another instance, max_irq_type is referring to the index while
num_irqs is referring to the count of vectors within this index.
VFIO_CCW_NUM_IRQS should only be used for max_irq_type.

> +		if (ret)
> +			return ret;
> +
> +		data = (void __user *)(arg + minsz);
> +		return vfio_ccw_mdev_set_irqs(mdev, hdr.flags, data);
> +	}
>  	case VFIO_DEVICE_RESET:
>  		return vfio_ccw_mdev_reset(mdev);
>  	default:
> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
> index 4621934..d551d98 100644
> --- a/drivers/s390/cio/vfio_ccw_private.h
> +++ b/drivers/s390/cio/vfio_ccw_private.h
> @@ -15,6 +15,7 @@
>  #define _VFIO_CCW_PRIVATE_H_
>  
>  #include <linux/completion.h>
> +#include <linux/eventfd.h>
>  #include <asm/vfio_ccw.h>
>  
>  #include "css.h"
> @@ -32,6 +33,7 @@
>   * @cp: ccw program for the current I/O operation
>   * @irb: irb info received from interrupt
>   * @scsw: scsw info
> + * @io_trigger: eventfd ctx for signaling userspace I/O results
>   */
>  struct vfio_ccw_private {
>  	struct subchannel	*sch;
> @@ -45,6 +47,8 @@ struct vfio_ccw_private {
>  	struct ccwprogram	cp;
>  	struct irb		irb;
>  	union scsw		scsw;
> +
> +	struct eventfd_ctx	*io_trigger;
>  } __aligned(8);
>  
>  extern int vfio_ccw_mdev_reg(struct subchannel *sch);
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 3fd70ff..ae46105 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -449,8 +449,9 @@ enum {
>  };
>  
>  /*
> - * The vfio-ccw bus driver makes use of the following fixed region.
> - * Unimplemented regions return a size of zero.
> + * The vfio-ccw bus driver makes use of the following fixed region and
> + * IRQ index mapping. Unimplemented regions return a size of zero.
> + * Unimplemented IRQ types return a count of zero.
>   */
>  
>  enum {
> @@ -458,6 +459,11 @@ enum {
>  	VFIO_CCW_NUM_REGIONS
>  };
>  
> +enum {
> +	VFIO_CCW_IO_IRQ_INDEX,
> +	VFIO_CCW_NUM_IRQS
> +};
> +
>  /**
>   * VFIO_DEVICE_GET_PCI_HOT_RESET_INFO - _IORW(VFIO_TYPE, VFIO_BASE + 12,
>   *					      struct vfio_pci_hot_reset_info)