linux-kernel - Re: [PATCH v3 7/7] dmaengine/idxd: Re-enable kernel workqueue under DMA API

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Message-ID: <ZC1mUKH/03QhkcR9@nvidia.com>
Date:   Wed, 5 Apr 2023 09:15:12 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Robin Murphy <robin.murphy@....com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, dmaengine@...r.kernel.org,
        vkoul@...nel.org, Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>
Subject: Re: [PATCH v3 7/7] dmaengine/idxd: Re-enable kernel workqueue under
 DMA API

On Fri, Mar 31, 2023 at 04:11:37PM -0700, Jacob Pan wrote:
>  static void idxd_disable_system_pasid(struct idxd_device *idxd)
>  {
> +	struct pci_dev *pdev = idxd->pdev;
> +	struct device *dev = &pdev->dev;
> +	struct iommu_domain *domain;
> +	union gencfg_reg gencfg;
> +
> +	domain = iommu_get_domain_for_dev(dev);
> +	if (!domain || domain->type == IOMMU_DOMAIN_BLOCKED)
> +		return;
> +
> +	iommu_detach_device_pasid(domain, dev, idxd->pasid);

This sequence is kinda weird, we shouldn't pass in domain to
detach_device_pasid, IMHO. We already know the domain because we store
it in an xarray, it just creates weirdness if the user passes in the
wrong domain.

Jason