linux-kernel - Re: [PATCH 2/2] iommu/sva: Remove mm parameter from SVA bind API

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Message-ID: <f29495e1-e3a0-8c45-bfca-067c1e996eca@linux.intel.com>
Date:   Fri, 9 Apr 2021 20:45:22 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>
Cc:     baolu.lu@...ux.intel.com, Yi Liu <yi.l.liu@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Dave Jiang <dave.jiang@...el.com>, wangzhou1@...ilicon.com,
        zhangfei.gao@...aro.org, vkoul@...nel.org
Subject: Re: [PATCH 2/2] iommu/sva: Remove mm parameter from SVA bind API

Hi,

On 2021/4/9 1:08, Jacob Pan wrote:
>   /**
>    * iommu_sva_alloc_pasid - Allocate a PASID for the mm
> - * @mm: the mm
>    * @min: minimum PASID value (inclusive)
>    * @max: maximum PASID value (inclusive)
>    *
> - * Try to allocate a PASID for this mm, or take a reference to the existing one
> - * provided it fits within the [@min, @max] range. On success the PASID is
> - * available in mm->pasid, and must be released with iommu_sva_free_pasid().
> + * Try to allocate a PASID for the current mm, or take a reference to the
> + * existing one provided it fits within the [@min, @max] range. On success
> + * the PASID is available in the current mm->pasid, and must be released with
> + * iommu_sva_free_pasid().
>    * @min must be greater than 0, because 0 indicates an unused mm->pasid.
>    *
>    * Returns 0 on success and < 0 on error.
>    */
> -int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> +int iommu_sva_alloc_pasid(ioasid_t min, ioasid_t max)
>   {
>   	int ret = 0;
>   	ioasid_t pasid;
> +	struct mm_struct *mm;
>   
>   	if (min == INVALID_IOASID || max == INVALID_IOASID ||
>   	    min == 0 || max < min)
>   		return -EINVAL;
>   
>   	mutex_lock(&iommu_sva_lock);
> +	mm = get_task_mm(current);

How could we allocate a supervisor PASID through iommu_sva_alloc_pasid()
if we always use current->mm here?

> +	if (!mm) {
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
>   	if (mm->pasid) {
>   		if (mm->pasid >= min && mm->pasid <= max)
>   			ioasid_get(mm->pasid);
> @@ -45,22 +51,32 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
>   		else
>   			mm->pasid = pasid;
>   	}
> +	mmput(mm);
> +out_unlock:
>   	mutex_unlock(&iommu_sva_lock);
>   	return ret;
>   }
>   EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);

Best regards,
baolu