linux-kernel - Re: [PATCH v2 12/13] vfio/type1: use iommu_attach

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Date:   Wed, 25 Sep 2019 20:37:16 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Liu Yi L <yi.l.liu@...el.com>
Cc:     kwankhede@...dia.com, kevin.tian@...el.com,
        baolu.lu@...ux.intel.com, yi.y.sun@...el.com, joro@...tes.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        yan.y.zhao@...el.com, shaopeng.he@...el.com, chenbo.xia@...el.com,
        jun.j.tian@...el.com
Subject: Re: [PATCH v2 12/13] vfio/type1: use iommu_attach_group() for
 wrapping PF/VF as mdev

On Thu,  5 Sep 2019 15:59:29 +0800
Liu Yi L <yi.l.liu@...el.com> wrote:

> This patch uses iommu_attach_group() to do group attach when it is
> for the case of wrapping a PF/VF as a mdev. iommu_attach_device()
> doesn't support non-singleton iommu group attach. With this change,
> wrapping PF/VF as mdev can work on non-singleton iommu groups.
> 
> Cc: Kevin Tian <kevin.tian@...el.com>
> Cc: Lu Baolu <baolu.lu@...ux.intel.com>
> Suggested-by: Alex Williamson <alex.williamson@...hat.com>
> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 054391f..317430d 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1312,13 +1312,20 @@ static int vfio_mdev_attach_domain(struct device *dev, void *data)
>  {
>  	struct iommu_domain *domain = data;
>  	struct device *iommu_device;
> +	struct iommu_group *group;
>  
>  	iommu_device = vfio_mdev_get_iommu_device(dev);
>  	if (iommu_device) {
>  		if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
>  			return iommu_aux_attach_device(domain, iommu_device);
> -		else
> -			return iommu_attach_device(domain, iommu_device);
> +		else {
> +			group = iommu_group_get(iommu_device);
> +			if (!group) {
> +				WARN_ON(1);

What's the value of the WARN_ON here and below?

iommu_group_get() increments the kobject reference, looks like it's
leaked.  Thanks,

Alex

> +				return -EINVAL;
> +			}
> +			return iommu_attach_group(domain, group);
> +		}
>  	}
>  
>  	return -EINVAL;
> @@ -1328,13 +1335,20 @@ static int vfio_mdev_detach_domain(struct device *dev, void *data)
>  {
>  	struct iommu_domain *domain = data;
>  	struct device *iommu_device;
> +	struct iommu_group *group;
>  
>  	iommu_device = vfio_mdev_get_iommu_device(dev);
>  	if (iommu_device) {
>  		if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
>  			iommu_aux_detach_device(domain, iommu_device);
> -		else
> -			iommu_detach_device(domain, iommu_device);
> +		else {
> +			group = iommu_group_get(iommu_device);
> +			if (!group) {
> +				WARN_ON(1);
> +				return -EINVAL;
> +			}
> +			iommu_detach_group(domain, group);
> +		}
>  	}
>  
>  	return 0;