linux-kernel - RE: [PATCH v10 6/7] iommu/vt-d: Add set_dev

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Message-ID: <BN9PR11MB52765154883041A3C0343A6E8C39A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Wed, 19 Jul 2023 05:39:57 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Robin Murphy" <robin.murphy@....com>
CC:     Jason Gunthorpe <jgg@...dia.com>, Will Deacon <will@...nel.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>
Subject: RE: [PATCH v10 6/7] iommu/vt-d: Add set_dev_pasid callback for dma
 domain

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Friday, July 14, 2023 2:00 PM
> 
> On 2023/7/14 11:50, Tian, Kevin wrote:
> >> From: Baolu Lu <baolu.lu@...ux.intel.com>
> >> Sent: Friday, July 14, 2023 11:34 AM
> >>
> >> On 2023/7/13 15:56, Tian, Kevin wrote:
> >>>> From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> >>>> Sent: Thursday, July 13, 2023 12:34 AM
> >>>>
> >>>>
> >>>> -	/*
> >>>> -	 * Should never reach here until we add support for attaching
> >>>> -	 * non-SVA domain to a pasid.
> >>>> -	 */
> >>>> -	WARN_ON(1);
> >>>> +	dmar_domain = to_dmar_domain(domain);
> >>>> +	spin_lock_irqsave(&dmar_domain->lock, flags);
> >>>> +	list_for_each_entry(curr, &dmar_domain->dev_pasids, link_domain)
> >>>> {
> >>>> +		if (curr->dev == dev && curr->pasid == pasid) {
> >>>> +			list_del(&curr->link_domain);
> >>>> +			dev_pasid = curr;
> >>>> +			break;
> >>>> +		}
> >>>> +	}
> >>>> +	spin_unlock_irqrestore(&dmar_domain->lock, flags);
> >>>>
> >>>
> >>> what about no matching dev_pasid is find?
> >>
> >> kfree() can handle this gracefully.
> >
> > but what about domain_detach_iommu()? Is it correct to adjust
> > the refcnting when there is no matching dev_pasid?
> 
> You are right.
> 
> Logically, if we get a valid domain for a pasid, we should have a
> dev_pasid allocated for it. Perhaps, adding a check in the code will
> make the code more readable?
> 

yes