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

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Message-ID: <eb700675-f698-62e5-bbab-3d199ff58dcb@linux.intel.com>
Date:   Thu, 15 Apr 2021 13:33:24 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        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>,
        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 Jason,

On 4/14/21 7:26 PM, Jason Gunthorpe wrote:
> On Wed, Apr 14, 2021 at 02:22:09PM +0800, Lu Baolu wrote:
> 
>> I still worry about supervisor pasid allocation.
>>
>> If we use iommu_sva_alloc_pasid() to allocate a supervisor pasid, which
>> mm should the pasid be set? I've ever thought about passing &init_mm to
>> iommu_sva_alloc_pasid(). But if you add "mm != current->mm", this seems
>> not to work. Or do you prefer a separated interface for supervisor pasid
>> allocation/free?
> 
> Without a mm_struct it is not SVA, so don't use SVA APIs for whatever
> a 'supervisor pasid' is

The supervisor PASID has its mm_struct. The only difference is that the
device will set priv=1 in its DMA transactions with the PASID.

Best regards,
baolu