linux-kernel - Re: [PATCH v5 09/12] iommu: Make iommu_queue

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Message-ID: <20230922124303.GE13795@ziepe.ca>
Date:   Fri, 22 Sep 2023 09:43:03 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     "Liu, Jingqi" <jingqi.liu@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 09/12] iommu: Make iommu_queue_iopf() more generic

On Fri, Sep 22, 2023 at 10:44:45AM +0800, Baolu Lu wrote:

> > > > @@ -112,6 +110,7 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
> > > >    {
> > > >    	int ret;
> > > >    	struct iopf_group *group;
> > > > +	struct iommu_domain *domain;
> > > >    	struct iopf_fault *iopf, *next;
> > > >    	struct iommu_fault_param *iopf_param;
> > > >    	struct dev_iommu *param = dev->iommu;
> > > > @@ -143,6 +142,19 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
> > > >    		return 0;
> > > >    	}
> > > > +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
> > > > +		domain = iommu_get_domain_for_dev_pasid(dev, fault->prm.pasid, 0);
> > > > +	else
> > > > +		domain = iommu_get_domain_for_dev(dev);
> > > > +
> > > > +	if (!domain || !domain->iopf_handler) {
> > > 
> > > Does it need to check if 'domain' is error ?  Like below:
> > > 
> > >           if (!domain || IS_ERR(domain) || !domain->iopf_handler)
> > 
> > Urk, yes, but not like that
> > 
> > The IF needs to be moved into the else block as each individual
> > function has its own return convention.
> 
> iommu_get_domain_for_dev_pasid() returns an ERR_PTR only if the matching
> domain type is specified (non-zero).
> 
> Adding IS_ERR(domain) in the else block will make the code more
> readable. Alternatively we can put a comment around above code to
> explain that ERR_PTR is not a case here.

You should check it because you'll probably get a static tool
complaint otherwise

Jason