linux-kernel - RE: [PATCH 07/12] iommu/vt-d: Acquiring lock in pasid manipulation helpers

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Date:   Wed, 1 Jun 2022 09:18:12 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Jason Gunthorpe" <jgg@...dia.com>
CC:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....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>
Subject: RE: [PATCH 07/12] iommu/vt-d: Acquiring lock in pasid manipulation
 helpers

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Friday, May 27, 2022 2:30 PM
> 
> The iommu->lock is used to protect the per-IOMMU pasid directory table
> and pasid table. Move the spinlock acquisition/release into the helpers
> to make the code self-contained.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>, with one nit

> 
> -	/* Caller must ensure PASID entry is not in use. */
> -	if (pasid_pte_is_present(pte))
> -		return -EBUSY;
> +	spin_lock(&iommu->lock);
> +	pte = get_non_present_pasid_entry(dev, pasid);
> +	if (!pte) {
> +		spin_unlock(&iommu->lock);
> +		return -ENODEV;
> +	}

I don't think above is a good abstraction and it changes the error
code for an present entry from -EBUSY to -ENODEV.