linux-kernel - Re: [PATCH 07/12] iommu/vt-d: Acquiring lock in pasid manipulation helpers

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Message-ID: <c70501f3-9cee-fc7d-4ebc-6f88e1ad147f@linux.intel.com>
Date:   Wed, 1 Jun 2022 18:48:23 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/12] iommu/vt-d: Acquiring lock in pasid manipulation
 helpers

On 2022/6/1 17:18, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Friday, May 27, 2022 2:30 PM
>>
>> The iommu->lock is used to protect the per-IOMMU pasid directory table
>> and pasid table. Move the spinlock acquisition/release into the helpers
>> to make the code self-contained.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> 
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>, with one nit
> 
>>
>> -	/* Caller must ensure PASID entry is not in use. */
>> -	if (pasid_pte_is_present(pte))
>> -		return -EBUSY;
>> +	spin_lock(&iommu->lock);
>> +	pte = get_non_present_pasid_entry(dev, pasid);
>> +	if (!pte) {
>> +		spin_unlock(&iommu->lock);
>> +		return -ENODEV;
>> +	}
> 
> I don't think above is a good abstraction and it changes the error
> code for an present entry from -EBUSY to -ENODEV.

Sure. I will roll it back to -EBUSY. I added this helper because the
same code appears at least three times in this file.

Best regards,
baolu