Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <64954f2d-2274-410e-269c-84efc0635633@linux.intel.com>
Date:   Thu, 12 May 2022 13:17:08 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.1
Cc:     baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
        Christoph Hellwig <hch@infradead.org>,
        "Raj, Ashok" <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        Vinod Koul <vkoul@kernel.org>,
        Eric Auger <eric.auger@redhat.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
        "Pan, Jacob jun" <jacob.jun.pan@intel.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 08/12] iommu/sva: Use attach/detach_pasid_dev in SVA
 interfaces
Content-Language: en-US
To:     "Tian, Kevin" <kevin.tian@intel.com>,
        Jason Gunthorpe <jgg@nvidia.com>
References: <20220510061738.2761430-1-baolu.lu@linux.intel.com>
 <20220510061738.2761430-9-baolu.lu@linux.intel.com>
 <20220510152330.GG49344@nvidia.com>
 <749a7d62-3e6c-ef5c-beaf-6b7add495740@linux.intel.com>
 <20220511145319.GZ49344@nvidia.com>
 <05a68e1e-8e18-5914-ebe7-d7b1a4aaa2ec@linux.intel.com>
 <BN9PR11MB5276C03134A898CA9EFEE9258CCB9@BN9PR11MB5276.namprd11.prod.outlook.com>
From:   Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <BN9PR11MB5276C03134A898CA9EFEE9258CCB9@BN9PR11MB5276.namprd11.prod.outlook.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2022/5/12 13:01, Tian, Kevin wrote:
>> From: Baolu Lu <baolu.lu@linux.intel.com>
>> Sent: Thursday, May 12, 2022 11:03 AM
>>
>> On 2022/5/11 22:53, Jason Gunthorpe wrote:
>>>>> Also, given the current arrangement it might make sense to have a
>>>>> struct iommu_domain_sva given that no driver is wrappering this in
>>>>> something else.
>>>> Fair enough. How about below wrapper?
>>>>
>>>> +struct iommu_sva_domain {
>>>> +       /*
>>>> +        * Common iommu domain header,*must*  be put at the top
>>>> +        * of the structure.
>>>> +        */
>>>> +       struct iommu_domain domain;
>>>> +       struct mm_struct *mm;
>>>> +       struct iommu_sva bond;
>>>> +}
>>>>
>>>> The refcount is wrapped in bond.
>>> I'm still not sure that bond is necessary
>>
>> "bond" is the sva handle that the device drivers get through calling
>> iommu_sva_bind().
>>
> 
> 'bond' was required before because we didn't have a domain to wrap
> the page table at that time.
> 
> Now we have a domain and it is 1:1 associated to bond. Probably
> make sense now by just returning the domain as the sva handle
> instead?

It also includes the device information that the domain has been
attached. So the sva_unbind() looks like this:

/**
  * iommu_sva_unbind_device() - Remove a bond created with 
iommu_sva_bind_device
  * @handle: the handle returned by iommu_sva_bind_device()
  *
  * Put reference to a bond between device and address space. The device 
should
  * not be issuing any more transaction for this PASID. All outstanding page
  * requests for this PASID must have been flushed to the IOMMU.
  */
void iommu_sva_unbind_device(struct iommu_sva *handle)

It's fine to replace the iommu_sva with iommu_sva_domain for sva handle,
if we can include the device in the unbind() interface.

Anyway, I'd expect to achieve all these in two steps:

- sva and iopf refactoring, only iommu internal changes;
- sva interface refactoring, only interface changes.

Does above work?

Best regards,
baolu