linux-kernel - Re: [PATCH 01/12] iommu/vt-d: Use iommu_get_domain_for

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Message-ID: <20220530121412.GX1343366@nvidia.com>
Date:   Mon, 30 May 2022 09:14:12 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/12] iommu/vt-d: Use iommu_get_domain_for_dev() in
 debugfs

On Sun, May 29, 2022 at 01:14:46PM +0800, Baolu Lu wrote:

> From 1e87b5df40c6ce9414cdd03988c3b52bfb17af5f Mon Sep 17 00:00:00 2001
> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Date: Sun, 29 May 2022 10:18:56 +0800
> Subject: [PATCH 1/1] iommu/vt-d: debugfs: Remove device_domain_lock usage
> 
> The domain_translation_struct debugfs node is used to dump static
> mappings of PCI devices. It potentially races with setting new
> domains to devices and the iommu_map/unmap() interfaces. The existing
> code tries to use the global spinlock device_domain_lock to avoid the
> races, but this is problematical as this lock is only used to protect
> the device tracking lists of the domains.
> 
> Instead of using an immature lock to cover up the problem, it's better
> to explicitly restrict the use of this debugfs node. This also makes
> device_domain_lock static.

What does "explicitly restrict" mean?

Jason