linux-kernel - RE: [PATCH 3/9] iommu: Add common code to handle IO page faults

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Message-ID: <BN9PR11MB52761F71BA509501C1766E9A8C31A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Tue, 11 Jul 2023 06:12:05 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Will Deacon" <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "Jason Gunthorpe" <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>
CC:     "Liu, Yi L" <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/9] iommu: Add common code to handle IO page faults

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Tuesday, July 11, 2023 9:07 AM
> 
> +static int iommu_handle_io_pgfault(struct device *dev,
> +				   struct iommu_fault *fault)
> +{
> +	struct iommu_domain *domain;
> +
> +	if (fault->type != IOMMU_FAULT_PAGE_REQ)
> +		return -EINVAL;
> +
> +	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)
> +		return -ENODEV;
> +
> +	if (domain->iopf_handler == iommu_sva_handle_iopf)
> +		return iommu_queue_iopf(fault, dev);

You can avoid the special check by directly making iommu_queue_iopf
as the iopf_handler for sva domain.

> +
> +	return domain->iopf_handler(fault, dev, domain->fault_data);
> +}

btw is there value of moving the group handling logic from
iommu_queue_iopf() to this common function?

I wonder whether there is any correctness issue if not forwarding
partial request to iommufd. If not this can also help reduce
notifications to the user until the group is ready.