linux-kernel - Re: [PATCH v2 1/4] drivers/iommu: Add page_ext for IOMMU_DEBUG

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Message-ID: <55391dad-339b-47f8-8996-afe337b238e0@infradead.org>
Date: Thu, 6 Nov 2025 11:50:11 -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, Qinxin Xia <xiaqinxin@...wei.com>
Subject: Re: [PATCH v2 1/4] drivers/iommu: Add page_ext for
 IOMMU_DEBUG_PAGEALLOC



> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 70d29b14d851..6b5e9a2d936a 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -383,4 +383,19 @@ config SPRD_IOMMU
>  
>  	  Say Y here if you want to use the multimedia devices listed above.
>  
> +config IOMMU_DEBUG_PAGEALLOC
> +	bool "Debug page memory allocations against IOMMU"
> +	depends on DEBUG_PAGEALLOC && IOMMU_API && PAGE_EXTENSION
> +	help
> +	  This config checks that a page is freed(unmapped) or mapped by the
> +	  kernel is not mapped in any IOMMU domain. It can help with debugging
> +	  use-after-free or out-of-bound maps from drivers doing DMA through
> +	  the IOMMU API.
> +	  This santaizer can have false-negative cases where some problems

	       sanitizer

> +	  won't be detected.
> +	  Expect overhead when enabling this and enabling the kernel command
> +	  line iommu.debug_pagealloc.
> +
> +	  If unsure, say N here.
> +
>  endif # IOMMU_SUPPORT


-- 
~Randy