linux-kernel - Re: [PATCH v5 7/9] iommufd: Associate fault object with iommufd_hw

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Date: Mon, 20 May 2024 10:18:49 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Nicolin Chen <nicolinc@...dia.com>, "Liu, Yi L" <yi.l.liu@...el.com>,
 Jacob Pan <jacob.jun.pan@...ux.intel.com>,
 Joel Granados <j.granados@...sung.com>
Cc: baolu.lu@...ux.intel.com, "iommu@...ts.linux.dev"
 <iommu@...ts.linux.dev>,
 "virtualization@...ts.linux-foundation.org"
 <virtualization@...ts.linux-foundation.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 7/9] iommufd: Associate fault object with
 iommufd_hw_pgtable

On 5/15/24 4:50 PM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Tuesday, April 30, 2024 10:57 PM
>>
>> @@ -227,7 +233,7 @@ iommufd_hwpt_nested_alloc(struct iommufd_ctx
>> *ictx,
>>   	refcount_inc(&parent->common.obj.users);
>>   	hwpt_nested->parent = parent;
>>
>> -	hwpt->domain = ops->domain_alloc_user(idev->dev, flags,
>> +	hwpt->domain = ops->domain_alloc_user(idev->dev, 0,
>>   					      parent->common.domain,
>> user_data);
> 
> it reads slightly better to clear the fault bit and still pass in flags.
> 

Done.

-       hwpt->domain = ops->domain_alloc_user(idev->dev, 0,
+       hwpt->domain = ops->domain_alloc_user(idev->dev,
+                                             flags & 
~IOMMU_HWPT_FAULT_ID_VALID,
                                               parent->common.domain, 
user_data);

>> @@ -308,6 +314,19 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd
>> *ucmd)
>>   		goto out_put_pt;
>>   	}
>>
>> +	if (cmd->flags & IOMMU_HWPT_FAULT_ID_VALID) {
>> +		struct iommufd_fault *fault;
>> +
>> +		fault = iommufd_get_fault(ucmd, cmd->fault_id);
>> +		if (IS_ERR(fault)) {
>> +			rc = PTR_ERR(fault);
>> +			goto out_hwpt;
>> +		}
>> +		hwpt->fault = fault;
>> +		hwpt->domain->iopf_handler = iommufd_fault_iopf_handler;
>> +		hwpt->domain->fault_data = hwpt;
>> +	}
> 
> this is nesting specific. why not moving it to the nested_alloc()?

Nesting is currently a use case for userspace I/O page faults, but this
design should be general enough to support other scenarios as well.

Best regards,
baolu