Re: [PATCH v4 1/4] iommu: Add page_ext for IOMMU_DEBUG_PAGEALLOC

[Baolu Lu <baolu.lu@linux.intel.com>]

On 12/11/25 20:59, 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@google.com>
> ---
>   .../admin-guide/kernel-parameters.txt         |  9 ++++++
>   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, 82 insertions(+)
>   create mode 100644 drivers/iommu/iommu-debug-pagealloc.c
>   create mode 100644 include/linux/iommu-debug-pagealloc.h

Do you need to update the MAINTAINERS file, since a new file (iommu-
debug-pagealloc.h) is being added?

> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index a8d0afde7f85..d484d9d8d0a4 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2675,6 +2675,15 @@ Kernel parameters
>   			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 behaves the same way as a kernel
> +			built without CONFIG_IOMMU_DEBUG_PAGEALLOC.
> +			Format: { "0" | "1" }
> +			0 - Sanitizer disabled.
> +			1 - Sanitizer enabled, expect runtime overhead.

"iommu.debug_pagealloc=0" has the same meaning as "unset". Would
"iommu=debug_pagealloc" look more appropriate?

> +
>   	io7=		[HW] IO7 for Marvel-based Alpha systems
>   			See comment before marvel_specify_io7 in
>   			arch/alpha/kernel/core_marvel.c.

[ ... ]

Other changes look good to me.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>