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Subject: Re: [PATCH v6 06/10] vfio/fsl-mc: Added lock support in preparation
 for interrupt handling
To:     Diana Craciun <diana.craciun@oss.nxp.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        kvm@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, bharatb.linux@gmail.com,
        laurentiu.tudor@nxp.com
References: <20201005173654.31773-1-diana.craciun@oss.nxp.com>
 <20201005173654.31773-7-diana.craciun@oss.nxp.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <ac58c7ea-6fe3-05dc-ee6d-19475a383736@redhat.com>
Date:   Sat, 10 Oct 2020 19:39:13 +0200
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Hi Diana,
On 10/5/20 7:36 PM, Diana Craciun wrote:
> Only the DPRC object allocates interrupts from the MSI
> interrupt domain. The interrupts are managed by the DPRC in
> a pool of interrupts. The access to this pool of interrupts
> has to be protected with a lock.
> This patch extends the current lock implementation to have a
> lock per DPRC.
> 
> Signed-off-by: Diana Craciun <diana.craciun@oss.nxp.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> ---
>  drivers/vfio/fsl-mc/vfio_fsl_mc.c         | 92 +++++++++++++++++++++--
>  drivers/vfio/fsl-mc/vfio_fsl_mc_private.h |  7 +-
>  2 files changed, 90 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> index 55190a2730fb..b52407c4e1ea 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> @@ -17,6 +17,78 @@
>  
>  static struct fsl_mc_driver vfio_fsl_mc_driver;
>  
> +static DEFINE_MUTEX(reflck_lock);
> +
> +static void vfio_fsl_mc_reflck_get(struct vfio_fsl_mc_reflck *reflck)
> +{
> +	kref_get(&reflck->kref);
> +}
> +
> +static void vfio_fsl_mc_reflck_release(struct kref *kref)
> +{
> +	struct vfio_fsl_mc_reflck *reflck = container_of(kref,
> +						      struct vfio_fsl_mc_reflck,
> +						      kref);
> +
> +	mutex_destroy(&reflck->lock);
> +	kfree(reflck);
> +	mutex_unlock(&reflck_lock);
> +}
> +
> +static void vfio_fsl_mc_reflck_put(struct vfio_fsl_mc_reflck *reflck)
> +{
> +	kref_put_mutex(&reflck->kref, vfio_fsl_mc_reflck_release, &reflck_lock);
> +}
> +
> +static struct vfio_fsl_mc_reflck *vfio_fsl_mc_reflck_alloc(void)
> +{
> +	struct vfio_fsl_mc_reflck *reflck;
> +
> +	reflck = kzalloc(sizeof(*reflck), GFP_KERNEL);
> +	if (!reflck)
> +		return ERR_PTR(-ENOMEM);
> +
> +	kref_init(&reflck->kref);
> +	mutex_init(&reflck->lock);
> +
> +	return reflck;
> +}
> +
> +static int vfio_fsl_mc_reflck_attach(struct vfio_fsl_mc_device *vdev)
> +{
> +	int ret;
> +
> +	mutex_lock(&reflck_lock);
> +	if (is_fsl_mc_bus_dprc(vdev->mc_dev)) {
> +		vdev->reflck = vfio_fsl_mc_reflck_alloc();
> +		ret = PTR_ERR_OR_ZERO(vdev->reflck);
> +	} else {
> +		struct device *mc_cont_dev = vdev->mc_dev->dev.parent;
> +		struct vfio_device *device;
> +		struct vfio_fsl_mc_device *cont_vdev;
> +
> +		device = vfio_device_get_from_dev(mc_cont_dev);
> +		if (!device) {
> +			ret = -ENODEV;
> +			goto unlock;
> +		}
> +
> +		cont_vdev = vfio_device_data(device);
> +		if (!cont_vdev || !cont_vdev->reflck) {
> +			vfio_device_put(device);
> +			ret = -ENODEV;
> +			goto unlock;
> +		}
> +		vfio_fsl_mc_reflck_get(cont_vdev->reflck);
> +		vdev->reflck = cont_vdev->reflck;
> +		vfio_device_put(device);
> +	}
> +
> +unlock:
> +	mutex_unlock(&reflck_lock);
> +	return ret;
> +}
> +
>  static int vfio_fsl_mc_regions_init(struct vfio_fsl_mc_device *vdev)
>  {
>  	struct fsl_mc_device *mc_dev = vdev->mc_dev;
> @@ -62,7 +134,7 @@ static int vfio_fsl_mc_open(void *device_data)
>  	if (!try_module_get(THIS_MODULE))
>  		return -ENODEV;
>  
> -	mutex_lock(&vdev->driver_lock);
> +	mutex_lock(&vdev->reflck->lock);
>  	if (!vdev->refcnt) {
>  		ret = vfio_fsl_mc_regions_init(vdev);
>  		if (ret)
> @@ -70,12 +142,12 @@ static int vfio_fsl_mc_open(void *device_data)
>  	}
>  	vdev->refcnt++;
>  
> -	mutex_unlock(&vdev->driver_lock);
> +	mutex_unlock(&vdev->reflck->lock);
>  
>  	return 0;
>  
>  err_reg_init:
> -	mutex_unlock(&vdev->driver_lock);
> +	mutex_unlock(&vdev->reflck->lock);
>  	module_put(THIS_MODULE);
>  	return ret;
>  }
> @@ -84,12 +156,12 @@ static void vfio_fsl_mc_release(void *device_data)
>  {
>  	struct vfio_fsl_mc_device *vdev = device_data;
>  
> -	mutex_lock(&vdev->driver_lock);
> +	mutex_lock(&vdev->reflck->lock);
>  
>  	if (!(--vdev->refcnt))
>  		vfio_fsl_mc_regions_cleanup(vdev);
>  
> -	mutex_unlock(&vdev->driver_lock);
> +	mutex_unlock(&vdev->reflck->lock);
>  
>  	module_put(THIS_MODULE);
>  }
> @@ -343,14 +415,18 @@ static int vfio_fsl_mc_probe(struct fsl_mc_device *mc_dev)
>  		goto out_group_put;
>  	}
>  
> -	ret = vfio_fsl_mc_init_device(vdev);
> +	ret = vfio_fsl_mc_reflck_attach(vdev);
>  	if (ret)
>  		goto out_group_dev;
>  
> -	mutex_init(&vdev->driver_lock);
> +	ret = vfio_fsl_mc_init_device(vdev);
> +	if (ret)
> +		goto out_reflck;
>  
>  	return 0;
>  
> +out_reflck:
> +	vfio_fsl_mc_reflck_put(vdev->reflck);
>  out_group_dev:
>  	vfio_del_group_dev(dev);
>  out_group_put:
> @@ -367,7 +443,7 @@ static int vfio_fsl_mc_remove(struct fsl_mc_device *mc_dev)
>  	if (!vdev)
>  		return -EINVAL;
>  
> -	mutex_destroy(&vdev->driver_lock);
> +	vfio_fsl_mc_reflck_put(vdev->reflck);
>  
>  	if (is_fsl_mc_bus_dprc(mc_dev)) {
>  		dprc_remove_devices(mc_dev, NULL, 0);
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h b/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
> index be60f41af30f..d47ef6215429 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
> @@ -15,6 +15,11 @@
>  #define VFIO_FSL_MC_INDEX_TO_OFFSET(index)	\
>  	((u64)(index) << VFIO_FSL_MC_OFFSET_SHIFT)
>  
> +struct vfio_fsl_mc_reflck {
> +	struct kref		kref;
> +	struct mutex		lock;
> +};
> +
>  struct vfio_fsl_mc_region {
>  	u32			flags;
>  	u32			type;
> @@ -27,7 +32,7 @@ struct vfio_fsl_mc_device {
>  	struct notifier_block        nb;
>  	int				refcnt;
>  	struct vfio_fsl_mc_region	*regions;
> -	struct mutex driver_lock;
> +	struct vfio_fsl_mc_reflck   *reflck;
>  };
>  
>  #endif /* VFIO_FSL_MC_PRIVATE_H */
>