linux-kernel - Re: [PATCH 5/9] iommu: Make fault

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Date:   Wed, 12 Jul 2023 11:02:50 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>, iommu@...ts.linux.dev,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] iommu: Make fault_param generic

On 2023/7/12 5:31, Jacob Pan wrote:
> On Tue, 11 Jul 2023 09:06:38 +0800, Lu Baolu<baolu.lu@...ux.intel.com>
> wrote:
> 
>> The iommu faults, including recoverable faults (IO page faults) and
>> unrecoverable faults (DMA faults), are generic to all devices. The
>> iommu faults could possibly be triggered for every device.
>>
>> The fault_param pointer under struct dev_iommu is the per-device fault
>> data. Therefore, the fault_param pointer should be allocated during
>> iommu device probe and freed when the device is released.
>>
>> With this done, the individual iommu drivers that support iopf have no
>> need to call iommu_[un]register_device_fault_handler() any more.
>> This will make it easier for the iommu drivers to support iopf, and it
>> will also make the fault_param allocation and free simpler.
>>
>> Signed-off-by: Lu Baolu<baolu.lu@...ux.intel.com>
>> ---
>>   .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c    | 13 +------------
>>   drivers/iommu/intel/iommu.c                    | 18 ++++--------------
>>   drivers/iommu/iommu.c                          | 14 ++++++++++++++
>>   3 files changed, 19 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c index
>> a5a63b1c947e..fa8ab9d413f8 100644 ---
>> a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c +++
>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c @@ -437,7 +437,6 @@
>> bool arm_smmu_master_sva_enabled(struct arm_smmu_master *master)
>>   static int arm_smmu_master_sva_enable_iopf(struct arm_smmu_master
>> *master) {
>> -	int ret;
>>   	struct device *dev = master->dev;
>>   
>>   	/*
>> @@ -450,16 +449,7 @@ static int arm_smmu_master_sva_enable_iopf(struct
>> arm_smmu_master *master) if (!master->iopf_enabled)
>>   		return -EINVAL;
>>   
>> -	ret = iopf_queue_add_device(master->smmu->evtq.iopf, dev);
>> -	if (ret)
>> -		return ret;
>> -
>> -	ret = iommu_register_device_fault_handler(dev, iommu_queue_iopf,
>> dev);
>> -	if (ret) {
>> -		iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
>> -		return ret;
>> -	}
>> -	return 0;
>> +	return iopf_queue_add_device(master->smmu->evtq.iopf, dev);
>>   }
>>   
>>   static void arm_smmu_master_sva_disable_iopf(struct arm_smmu_master
>> *master) @@ -469,7 +459,6 @@ static void
>> arm_smmu_master_sva_disable_iopf(struct arm_smmu_master *master) if
>> (!master->iopf_enabled) return;
>>   
>> -	iommu_unregister_device_fault_handler(dev);
>>   	iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
>>   }
>>   
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index 5c8c5cdc36cf..22e43db20252 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -4594,23 +4594,14 @@ static int intel_iommu_enable_iopf(struct device
>> *dev) if (ret)
>>   		return ret;
>>   
>> -	ret = iommu_register_device_fault_handler(dev, iommu_queue_iopf,
>> dev);
>> -	if (ret)
>> -		goto iopf_remove_device;
>> -
>>   	ret = pci_enable_pri(pdev, PRQ_DEPTH);
>> -	if (ret)
>> -		goto iopf_unregister_handler;
>> +	if (ret) {
>> +		iopf_queue_remove_device(iommu->iopf_queue, dev);
>> +		return ret;
>> +	}
>>   	info->pri_enabled = 1;
>>   
>>   	return 0;
>> -
>> -iopf_unregister_handler:
>> -	iommu_unregister_device_fault_handler(dev);
>> -iopf_remove_device:
>> -	iopf_queue_remove_device(iommu->iopf_queue, dev);
>> -
>> -	return ret;
>>   }
>>   
>>   static int intel_iommu_disable_iopf(struct device *dev)
>> @@ -4637,7 +4628,6 @@ static int intel_iommu_disable_iopf(struct device
>> *dev)
>>   	 * fault handler and removing device from iopf queue should never
>>   	 * fail.
>>   	 */
>> -	WARN_ON(iommu_unregister_device_fault_handler(dev));
>>   	WARN_ON(iopf_queue_remove_device(iommu->iopf_queue, dev));
>>   
>>   	return 0;
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 65895b987e22..8d1f0935ea71 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -299,7 +299,15 @@ static int dev_iommu_get(struct device *dev)
>>   		return -ENOMEM;
>>   
>>   	mutex_init(&param->lock);
>> +	param->fault_param = kzalloc(sizeof(*param->fault_param),
>> GFP_KERNEL);
> since fault_param is_always_  allocated/freed along with param, can we merge
> into one allocation? i.e.
>   struct dev_iommu {
>          struct mutex lock;
> -       struct iommu_fault_param        *fault_param;
> +       struct iommu_fault_param        fault_param;

I am not pretty sure about the change in this patch. It's a simple-and-
stupid way. But it also wastes memory for devices that have not pri-
capable domain attached.

So probably it's better to allocate fault_param at the place where a
real pri-capable domain is attached to the device?

Best regards,
baolu