linux-kernel - Re: [PATCH v4 09/10] iommu: Make iommu_queue

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Message-ID: <3b893bf4-a566-9a1f-49da-17efdd7e4661@linux.intel.com>
Date:   Sat, 26 Aug 2023 16:08:03 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>
Cc:     baolu.lu@...ux.intel.com, "Liu, Yi L" <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 09/10] iommu: Make iommu_queue_iopf() more generic

On 8/25/23 4:17 PM, Tian, Kevin wrote:
>> +
>> +	list_for_each_entry(iopf, &iopf_param->faults, list) {
>> +		if (WARN_ON(iopf->fault.prm.pasid == pasid))
>> +			break;
>> +	}
>> +	mutex_unlock(&iopf_param->lock);
>> +}
>> +
>>   void iommu_detach_device(struct iommu_domain *domain, struct device
>> *dev)
>>   {
>>   	struct iommu_group *group;
>> @@ -1959,6 +1980,7 @@ void iommu_detach_device(struct iommu_domain
>> *domain, struct device *dev)
>>   	if (!group)
>>   		return;
>>
>> +	assert_no_pending_iopf(dev, IOMMU_NO_PASID);
>>   	mutex_lock(&group->mutex);
>>   	if (WARN_ON(domain != group->domain) ||
>>   	    WARN_ON(list_count_nodes(&group->devices) != 1))
>> @@ -3269,6 +3291,7 @@ void iommu_detach_device_pasid(struct
>> iommu_domain *domain, struct device *dev,
>>   {
>>   	struct iommu_group *group = iommu_group_get(dev);
>>
>> +	assert_no_pending_iopf(dev, pasid);
> this doesn't look correct. A sane driver will stop triggering new
> page request before calling detach but there are still pending ones
> not drained until iopf_queue_flush_dev() called by
> ops->remove_dev_pasid().
> 
> then this check will cause false warning.
> 

You are right. It is not only incorrect but also pointless. The iommu
driver should flush the iopf queues in the path of detaching domains. I
will remove it if no objection.

Best regards,
baolu