linux-kernel - Re: [PATCH v3 3/5] iommu: Add iommu_get_domain_for_dev

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20250821183704.GP802098@nvidia.com>
Date: Thu, 21 Aug 2025 15:37:04 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: robin.murphy@....com, joro@...tes.org, bhelgaas@...gle.com,
	will@...nel.org, robin.clark@....qualcomm.com, yong.wu@...iatek.com,
	matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	rafael@...nel.org, lenb@...nel.org, kevin.tian@...el.com,
	yi.l.liu@...el.com, baolu.lu@...ux.intel.com,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-mediatek@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
	patches@...ts.linux.dev, pjaroszynski@...dia.com, vsethi@...dia.com,
	helgaas@...nel.org, etzhao1900@...il.com
Subject: Re: [PATCH v3 3/5] iommu: Add iommu_get_domain_for_dev_locked()
 helper

On Thu, Aug 21, 2025 at 08:22:06AM -0700, Nicolin Chen wrote:
> I should have pasted the full piece:
> drivers/gpu/drm/tegra/drm.c-960-	/*
> drivers/gpu/drm/tegra/drm.c:961:	 * If the host1x client is already attached to an IOMMU domain that is
> drivers/gpu/drm/tegra/drm.c-962-	 * not the shared IOMMU domain, don't try to attach it to a different
> drivers/gpu/drm/tegra/drm.c-963-	 * domain. This allows using the IOMMU-backed DMA API.
> drivers/gpu/drm/tegra/drm.c-964-	 */
> drivers/gpu/drm/tegra/drm.c-965-	if (domain && domain->type != IOMMU_DOMAIN_IDENTITY &&
> drivers/gpu/drm/tegra/drm.c-966-	    domain != tegra->domain)
> 
> So, the check is two-fold:
> 1) is attached
> 2) is the shared IOMMU domain (tegra->domain?)

Yea

 iommu_is_domain_currently_attached(dev, tegra->domain)

> Overall, I feel this would be a big project yet arguably for a low
> reward..

Indeed, we can drop a FIXME comment there and leave it as the last
user or something perhaps

Jason