linux-kernel - RE: [PATCH v10 5/7] iommu/vt-d: Make prq draining code generic

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Message-ID: <BN9PR11MB52763423F2A18E927065C8EA8C34A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Fri, 14 Jul 2023 03:49:00 +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 5/7] iommu/vt-d: Make prq draining code generic

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Friday, July 14, 2023 11:28 AM
> 
> On 2023/7/13 15:49, Tian, Kevin wrote:
> >> From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> >> Sent: Thursday, July 13, 2023 12:34 AM
> >>
> >> -	/* Domain type specific cleanup: */
> >>   	domain = iommu_get_domain_for_dev_pasid(dev, pasid, 0);
> >> -	if (domain) {
> >> -		switch (domain->type) {
> >> -		case IOMMU_DOMAIN_SVA:
> >> -			intel_svm_remove_dev_pasid(dev, pasid);
> >> -			break;
> >> -		default:
> >> -			/* should never reach here */
> >> -			WARN_ON(1);
> >> -			break;
> >> -		}
> >> +	if (!domain)
> >> +		goto out_tear_down;
> >
> > WARN_ON()
> 
> Why?
> 
> My understanding is that remve_device_pasid could be call in any context
> including no domain attached.
> 

oh I'm not aware of that. Can you elaborate the usage which uses a pasid
w/o domain? pasid needs to point to a page table. Presumably every
page table should be wrapped by a iommu domain...