linux-kernel - Re: [PATCH 9/9] iommu: Use fault cookie to store iopf

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Date:   Tue, 11 Jul 2023 15:02:49 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>, iommu@...ts.linux.dev,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 9/9] iommu: Use fault cookie to store iopf_param

Hi BaoLu,

On Tue, 11 Jul 2023 09:06:42 +0800, Lu Baolu <baolu.lu@...ux.intel.com>
wrote:

> Remove the static iopf_param pointer from struct iommu_fault_param to
> save memory.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  include/linux/iommu.h      |  2 --
>  drivers/iommu/io-pgfault.c | 47 +++++++++++++++++++++++---------------
>  2 files changed, 29 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index ffd6fe1317f4..5fe37a7c5a55 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -551,7 +551,6 @@ struct iommu_fault_param {
>   * struct dev_iommu - Collection of per-device IOMMU data
>   *
>   * @fault_param: IOMMU detected device fault reporting data
> - * @iopf_param:	 I/O Page Fault queue and data
>   * @fwspec:	 IOMMU fwspec data
>   * @iommu_dev:	 IOMMU device this device is linked to
>   * @priv:	 IOMMU Driver private data
> @@ -564,7 +563,6 @@ struct iommu_fault_param {
>  struct dev_iommu {
>  	struct mutex lock;
>  	struct iommu_fault_param	*fault_param;
> -	struct iopf_device_param	*iopf_param;
>  	struct iommu_fwspec		*fwspec;
>  	struct iommu_device		*iommu_dev;
>  	void				*priv;
> diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
> index 1749e0869f2e..6a3a4e08e67e 100644
> --- a/drivers/iommu/io-pgfault.c
> +++ b/drivers/iommu/io-pgfault.c
> @@ -158,7 +158,7 @@ int iommu_queue_iopf(struct iommu_fault *fault,
> struct device *dev)
>  	 * As long as we're holding param->lock, the queue can't be
> unlinked
>  	 * from the device and therefore cannot disappear.
>  	 */
> -	iopf_param = param->iopf_param;
> +	iopf_param = iommu_get_device_fault_cookie(dev, 0);
I am not sure I understand how does it know the cookie type is iopf_param
for PASID 0?

Between IOPF and IOMMUFD use of the cookie, cookie types are different,
right?

>  	if (!iopf_param)
>  		return -ENODEV;
>  
> @@ -235,7 +235,7 @@ int iopf_queue_flush_dev(struct device *dev)
>  		return -ENODEV;
>  
>  	mutex_lock(&param->lock);
> -	iopf_param = param->iopf_param;
> +	iopf_param = iommu_get_device_fault_cookie(dev, 0);
>  	if (iopf_param)
>  		flush_workqueue(iopf_param->queue->wq);
>  	else
> @@ -286,9 +286,9 @@ EXPORT_SYMBOL_GPL(iopf_queue_discard_partial);
>   */
>  int iopf_queue_add_device(struct iopf_queue *queue, struct device *dev)
>  {
> -	int ret = -EBUSY;
> -	struct iopf_device_param *iopf_param;
> +	struct iopf_device_param *iopf_param, *curr;
>  	struct dev_iommu *param = dev->iommu;
> +	int ret;
>  
>  	if (!param)
>  		return -ENODEV;
> @@ -303,16 +303,27 @@ int iopf_queue_add_device(struct iopf_queue *queue,
> struct device *dev) 
>  	mutex_lock(&queue->lock);
>  	mutex_lock(&param->lock);
> -	if (!param->iopf_param) {
> -		list_add(&iopf_param->queue_list, &queue->devices);
> -		param->iopf_param = iopf_param;
> -		ret = 0;
> +	curr = iommu_set_device_fault_cookie(dev, 0, iopf_param);
> +	if (IS_ERR(curr)) {
> +		ret = PTR_ERR(curr);
> +		goto err_free;
>  	}
> +
> +	if (curr) {
> +		ret = -EBUSY;
> +		goto err_restore;
> +	}
> +	list_add(&iopf_param->queue_list, &queue->devices);
>  	mutex_unlock(&param->lock);
>  	mutex_unlock(&queue->lock);
>  
> -	if (ret)
> -		kfree(iopf_param);
> +	return 0;
> +err_restore:
> +	iommu_set_device_fault_cookie(dev, 0, curr);
> +err_free:
> +	mutex_unlock(&param->lock);
> +	mutex_unlock(&queue->lock);
> +	kfree(iopf_param);
>  
>  	return ret;
>  }
> @@ -329,7 +340,6 @@ EXPORT_SYMBOL_GPL(iopf_queue_add_device);
>   */
>  int iopf_queue_remove_device(struct iopf_queue *queue, struct device
> *dev) {
> -	int ret = -EINVAL;
>  	struct iopf_fault *iopf, *next;
>  	struct iopf_device_param *iopf_param;
>  	struct dev_iommu *param = dev->iommu;
> @@ -339,16 +349,17 @@ int iopf_queue_remove_device(struct iopf_queue
> *queue, struct device *dev) 
>  	mutex_lock(&queue->lock);
>  	mutex_lock(&param->lock);
> -	iopf_param = param->iopf_param;
> -	if (iopf_param && iopf_param->queue == queue) {
> -		list_del(&iopf_param->queue_list);
> -		param->iopf_param = NULL;
> -		ret = 0;
> +	iopf_param = iommu_get_device_fault_cookie(dev, 0);
> +	if (!iopf_param || iopf_param->queue != queue) {
> +		mutex_unlock(&param->lock);
> +		mutex_unlock(&queue->lock);
> +		return -EINVAL;
>  	}
> +
> +	list_del(&iopf_param->queue_list);
> +	iommu_set_device_fault_cookie(dev, 0, NULL);
>  	mutex_unlock(&param->lock);
>  	mutex_unlock(&queue->lock);
> -	if (ret)
> -		return ret;
>  
>  	/* Just in case some faults are still stuck */
>  	list_for_each_entry_safe(iopf, next, &iopf_param->partial, list)


Thanks,

Jacob