linux-kernel - Re: [PATCH 3/9] iommu: Add common code to handle IO page faults

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Date:   Wed, 12 Jul 2023 10:37:03 +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 3/9] iommu: Add common code to handle IO page faults

On 2023/7/12 4:50, Jacob Pan wrote:
> Hi Lu,
> 
> On Tue, 11 Jul 2023 09:06:36 +0800, Lu Baolu <baolu.lu@...ux.intel.com>
> wrote:
> 
>> The individual iommu drivers report iommu faults by calling
>> iommu_report_device_fault(), where a pre-registered device fault handler
>> is called to route the fault to another fault handler installed on the
>> corresponding iommu domain.
>>
>> The pre-registered device fault handler is static and won't be dynamic
>> as the fault handler is eventually per iommu domain. Replace the device
>> fault handler with a static common code to avoid unnecessary code.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>>   drivers/iommu/iommu.c | 24 +++++++++++++++++++++++-
>>   1 file changed, 23 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index da340f11c5f5..41328f03e8b4 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -1278,6 +1278,28 @@ int iommu_unregister_device_fault_handler(struct
>> device *dev) }
>>   EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
>>   
>> +static int iommu_handle_io_pgfault(struct device *dev,
>> +				   struct iommu_fault *fault)
>> +{
>> +	struct iommu_domain *domain;
>> +
>> +	if (fault->type != IOMMU_FAULT_PAGE_REQ)
>> +		return -EINVAL;
>> +
>> +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
>> +		domain = iommu_get_domain_for_dev_pasid(dev,
>> fault->prm.pasid, 0);
>> +	else
>> +		domain = iommu_get_domain_for_dev(dev);
> we don't support IOPF w/o PASID yet, right?

It's the individual driver that decides whether iopf w/o pasid is
supported or not. The iommu core doesn't need to make such assumption.

> 
>> +
>> +	if (!domain || !domain->iopf_handler)
>> +		return -ENODEV;
>> +
>> +	if (domain->iopf_handler == iommu_sva_handle_iopf)
>> +		return iommu_queue_iopf(fault, dev);
> Just wondering why have a special treatment for SVA domain. Can
> iommu_queue_iopf() be used as SVA domain->iopf_handler?

Yes. I will make this change according to Kevin's suggestion in this
thread.

> 
>> +
>> +	return domain->iopf_handler(fault, dev, domain->fault_data);
>> +}
>> +
>>   /**
>>    * iommu_report_device_fault() - Report fault event to device driver
>>    * @dev: the device
>> @@ -1320,7 +1342,7 @@ int iommu_report_device_fault(struct device *dev,
>> struct iommu_fault_event *evt) mutex_unlock(&fparam->lock);
>>   	}
>>   
>> -	ret = fparam->handler(&evt->fault, fparam->data);
>> +	ret = iommu_handle_io_pgfault(dev, &evt->fault);
>>   	if (ret && evt_pending) {
>>   		mutex_lock(&fparam->lock);
>>   		list_del(&evt_pending->list);
> 
> 
> Thanks,
> 
> Jacob
> 

Best regards,
baolu