linux-kernel - Re: [PATCH v13 4/8] iommu/vt-d: Add bind guest PASID support

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Date:   Sat, 16 May 2020 14:02:23 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     baolu.lu@...ux.intel.com, iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Eric Auger <eric.auger@...hat.com>,
        Yi Liu <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH v13 4/8] iommu/vt-d: Add bind guest PASID support

Hi Jacob,

On 2020/5/14 23:57, Jacob Pan wrote:
> Hi Christoph,
> 
> Thanks a lot for the reviews, comments below.
> 
> Jacob
> 
> On Wed, 13 May 2020 22:59:30 -0700
> Christoph Hellwig<hch@...radead.org>  wrote:
> 
>>> +	if (dev_is_pci(dev)) {
>>> +		/* VT-d supports devices with full 20 bit PASIDs
>>> only */
>>> +		if (pci_max_pasids(to_pci_dev(dev)) != PASID_MAX)
>>> +			return -EINVAL;
>>> +	} else {
>>> +		return -ENOTSUPP;
>>> +	}
>> This looks strange.  Why not:
>>
>> 	if (!dev_is_pci(dev)) {
>> 		return -ENOTSUPP;
>>
>> 	/* VT-d supports devices with full 20 bit PASIDs only */
>> 	if (pci_max_pasids(to_pci_dev(dev)) != PASID_MAX)
>> 		return -EINVAL;
>>
> That is better, will do.
> 
>>> +		for_each_svm_dev(sdev, svm, dev) {
>>> +			/*
>>> +			 * For devices with aux domains, we should
>>> allow multiple
>>> +			 * bind calls with the same PASID and pdev.
>>> +			 */
>>> +			if (iommu_dev_feature_enabled(dev,
>>> IOMMU_DEV_FEAT_AUX)) {
>>> +				sdev->users++;
>>> +			} else {
>>> +				dev_warn_ratelimited(dev, "Already
>>> bound with PASID %u\n",
>>> +						svm->pasid);
>>> +				ret = -EBUSY;
>>> +			}
>>> +			goto out;
>> Is this intentionally a for loop that jumps out of the loop after
>> the first device?
>>
> The name is confusing, it is not a loop. I will change it to
> find_svm_dev() and comments like this?
> 
> /*
>   * Find the matching device in a given SVM. The bind code ensures that
>   * each device can only be added to the SVM list once.
>   */
> #define find_svm_dev(sdev, svm, d)			\
> 	list_for_each_entry((sdev), &(svm)->devs, list)	\
> 		if ((d) != (sdev)->dev) {} else
> 

The for_each_svm_dev() is not added by this series and is also used by
other functions. How about changing it in a separated patch?

Best regards,
baolu