linux-kernel - RE: [PATCH 1/1] iommu/vt-d: Fix RID2PASID setup failure

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Date:   Tue, 21 Jun 2022 03:46:38 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>
CC:     "Qiang, Chenyi" <chenyi.qiang@...el.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>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 1/1] iommu/vt-d: Fix RID2PASID setup failure

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Tuesday, June 21, 2022 11:39 AM
> 
> On 2022/6/21 10:54, Tian, Kevin wrote:
> >> From: Lu Baolu <baolu.lu@...ux.intel.com>
> >> Sent: Monday, June 20, 2022 4:17 PM
> >> @@ -2564,7 +2564,7 @@ static int domain_add_dev_info(struct
> >> dmar_domain *domain, struct device *dev)
> >>   			ret = intel_pasid_setup_second_level(iommu,
> >> domain,
> >>   					dev, PASID_RID2PASID);
> >>   		spin_unlock_irqrestore(&iommu->lock, flags);
> >> -		if (ret) {
> >> +		if (ret && ret != -EBUSY) {
> >>   			dev_err(dev, "Setup RID2PASID failed\n");
> >>   			dmar_remove_one_dev_info(dev);
> >>   			return ret;
> >> --
> >> 2.25.1
> >
> > It's cleaner to avoid this error at the first place, i.e. only do the
> > setup when the first device is attached to the pasid table.
> 
> The logic that identifies the first device might introduce additional
> unnecessary complexity. Devices that share a pasid table are rare. I
> even prefer to give up sharing tables so that the code can be
> simpler.:-)
> 

It's not that complex if you simply move device_attach_pasid_table()
out of intel_pasid_alloc_table(). Then do the setup if
list_empty(&pasid_table->dev) and then attach device to the
pasid table in domain_add_dev_info().