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

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Message-ID: <uwznrzdsbfpbalzf5jxxpguf2ykslphfs47u7gf66ssiwzpqju@dh7nw3van6sr>
Date: Mon, 27 Oct 2025 12:42:09 +0100
From: Jörg Rödel <joro@...tes.org>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: linux-mm@...ck.org, iommu@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, corbet@....net, 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
Subject: Re: [RFC PATCH 1/4] drivers/iommu: Add page_ext for
 IOMMU_DEBUG_PAGEALLOC

On Fri, Oct 03, 2025 at 05:32:26PM +0000, Mostafa Saleh wrote:
> +config IOMMU_DEBUG_PAGEALLOC
> +	bool "Debug page memory allocations against IOMMU"
> +	depends on DEBUG_PAGEALLOC && IOMMU_API && PAGE_EXTENSION
> +	help
> +		This config checks when a page is freed by the kernel
> +		it's not mapped in any IOMMU domain. It can help with
> +		debugging use-after-free from driver doing DMA.
> +		This santaizer can have false-negative cases where some
> +		problems won't be detected.
> +		Expect overhead when enabling this + enabling the kernel
> +		command line iommu.debug_pagealloc.
> +
> +		If unsure, say N here.

Expected indentation here is <tab><space><space> and not <tab><tab>.

> --- /dev/null
> +++ b/drivers/iommu/iommu-debug.c

Is there a plan for this file to contain more than page-alloc debugging? If
not, it should get a more specific name, like iommu-debug-pagealloc.c or
similar.