linux-kernel - Re: [PATCH v3 1/4] drivers/iommu: Add page_ext for IOMMU_DEBUG

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Message-ID: <7854489b-bc9e-4bb9-a19d-cff96badc180@infradead.org>
Date: Mon, 24 Nov 2025 15:13:22 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Mostafa Saleh <smostafa@...gle.com>, linux-mm@...ck.org,
 iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org
Cc: corbet@....net, joro@...tes.org, will@...nel.org, robin.murphy@....com,
 akpm@...ux-foundation.org, vbabka@...e.cz, surenb@...gle.com,
 mhocko@...e.com, jackmanb@...gle.com, hannes@...xchg.org, ziy@...dia.com,
 david@...hat.com, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com,
 rppt@...nel.org, xiaqinxin@...wei.com
Subject: Re: [PATCH v3 1/4] drivers/iommu: Add page_ext for
 IOMMU_DEBUG_PAGEALLOC



On 11/24/25 12:08 PM, Mostafa Saleh wrote:
> Add a new config IOMMU_DEBUG_PAGEALLOC, which registers new data to
> page_ext.
> 
> This config will be used by the IOMMU API to track pages mapped in
> the IOMMU to catch drivers trying to free kernel memory that they
> still map in their domains, causing all types of memory corruption.
> 
> This behaviour is disabled by default and can be enabled using
> kernel cmdline iommu.debug_pagealloc.
> 
> Signed-off-by: Mostafa Saleh <smostafa@...gle.com>
> ---
>  .../admin-guide/kernel-parameters.txt         |  6 ++++
>  drivers/iommu/Kconfig                         | 19 +++++++++++
>  drivers/iommu/Makefile                        |  1 +
>  drivers/iommu/iommu-debug-pagealloc.c         | 32 +++++++++++++++++++
>  include/linux/iommu-debug-pagealloc.h         | 17 ++++++++++
>  mm/page_ext.c                                 |  4 +++
>  6 files changed, 79 insertions(+)
>  create mode 100644 drivers/iommu/iommu-debug-pagealloc.c
>  create mode 100644 include/linux/iommu-debug-pagealloc.h
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 6c42061ca20e..dddf435a1c11 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2557,6 +2557,12 @@
>  			1 - Bypass the IOMMU for DMA.
>  			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
>  
> +	iommu.debug_pagealloc=
> +			[KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this
> +			parameter enables the feature at boot time. By default, it
> +			is disabled and the system behave the same way as a kernel

			                           behaves

> +			built without CONFIG_IOMMU_DEBUG_PAGEALLOC.
> +
>  	io7=		[HW] IO7 for Marvel-based Alpha systems
>  			See comment before marvel_specify_io7 in
>  			arch/alpha/kernel/core_marvel.c.


-- 
~Randy