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

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Date:   Fri, 9 Apr 2021 11:08:08 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.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,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 2/2] iommu/sva: Remove mm parameter from SVA bind API

Hi Lu,

On Fri, 9 Apr 2021 20:45:22 +0800, Lu Baolu <baolu.lu@...ux.intel.com>
wrote:

> > -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?
I don't think you can. But I guess the current callers of this function do
not need supervisor PASID.
In reply to Jean, I suggest we split this function into mm->pasid
assignment and keep using ioasid_alloc() directly, then supervisor PASID is
caller's bind choice.

Thanks,

Jacob