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Message-ID: <bd08d2b0-f226-4b42-8d3b-099c46435aa2@linux.intel.com>
Date: Mon, 20 May 2024 10:10:16 +0800
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Cc: baolu.lu@linux.intel.com, "iommu@lists.linux.dev"
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 "virtualization@lists.linux-foundation.org"
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Subject: Re: [PATCH v5 6/9] iommufd: Fault-capable hwpt attach/detach/replace
To: "Tian, Kevin" <kevin.tian@intel.com>, Jason Gunthorpe <jgg@ziepe.ca>,
 Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
 Robin Murphy <robin.murphy@arm.com>,
 Jean-Philippe Brucker <jean-philippe@linaro.org>,
 Nicolin Chen <nicolinc@nvidia.com>, "Liu, Yi L" <yi.l.liu@intel.com>,
 Jacob Pan <jacob.jun.pan@linux.intel.com>,
 Joel Granados <j.granados@samsung.com>
References: <20240430145710.68112-1-baolu.lu@linux.intel.com>
 <20240430145710.68112-7-baolu.lu@linux.intel.com>
 <BN9PR11MB5276D582749AD8B619B11B688CEC2@BN9PR11MB5276.namprd11.prod.outlook.com>
Content-Language: en-US
From: Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <BN9PR11MB5276D582749AD8B619B11B688CEC2@BN9PR11MB5276.namprd11.prod.outlook.com>
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On 5/15/24 4:43 PM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@linux.intel.com>
>> Sent: Tuesday, April 30, 2024 10:57 PM
>> +
>> +int iommufd_fault_domain_replace_dev(struct iommufd_device *idev,
>> +				     struct iommufd_hw_pagetable *hwpt,
>> +				     struct iommufd_hw_pagetable *old)
>> +{
>> +	struct iommu_attach_handle *handle;
>> +	int ret;
>> +
>> +	if (hwpt->fault)
>> +		ret = iommufd_fault_iopf_enable(idev);
>> +	else
>> +		iommufd_fault_iopf_disable(idev);
>> +
>> +	ret = iommu_group_replace_domain(idev->igroup->group, hwpt-
>>> domain);
>> +	if (ret)
>> +		goto out_cleanup;
>> +
>> +	iommufd_auto_response_faults(old, idev);
>> +	handle = iommu_attach_handle_get(idev->igroup->group,
>> IOMMU_NO_PASID, 0);
>> +	handle->idev = idev;
> 
> why is auto response required in replace? new requests can come
> after the auto response anyway...
> 
> The user should prepare for faults delivered to the old or new hwpt
> in the transition window.

The current design of replace allows switching between one that is not
IOPF-capable and one that is. This implies that if we switch from an
IOPF-capable hwpt to a non-IOPF-capable one, the response queue needs to
be auto responded.

Best regards,
baolu