linux-kernel - Re: [PATCH 01/11] iommu: Add device dma ownership set/release interfaces

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Message-ID: <cc7ce6f4-b1ec-49ef-e245-ab6c330154c2@linux.intel.com>
Date:   Tue, 16 Nov 2021 09:57:30 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     baolu.lu@...ux.intel.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Chaitanya Kulkarni <kch@...dia.com>, kvm@...r.kernel.org,
        rafael@...nel.org, linux-pci@...r.kernel.org,
        Cornelia Huck <cohuck@...hat.com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Diana Craciun <diana.craciun@....nxp.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH 01/11] iommu: Add device dma ownership set/release
 interfaces

Hi Christoph,

On 11/15/21 9:14 PM, Christoph Hellwig wrote:
> On Mon, Nov 15, 2021 at 10:05:42AM +0800, Lu Baolu wrote:
>> +enum iommu_dma_owner {
>> +	DMA_OWNER_NONE,
>> +	DMA_OWNER_KERNEL,
>> +	DMA_OWNER_USER,
>> +};
>> +
> 
>> +	enum iommu_dma_owner dma_owner;
>> +	refcount_t owner_cnt;
>> +	struct file *owner_user_file;
> 
> I'd just overload the ownership into owner_user_file,
> 
>   NULL			-> no owner
>   (struct file *)1UL)	-> kernel
>   real pointer		-> user
> 
> Which could simplify a lot of the code dealing with the owner.
> 

Yeah! Sounds reasonable. I will make this in the next version.

Best regards,
baolu