Re: [PATCH 01/12] iommu/vt-d: Use iommu_get_domain_for_dev() in debugfs

Jason Gunthorpe via iommu
2022-05-30T12:14:21Z

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@linux.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