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

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Message-ID: <aSQ7xfQjkeAMHiLC@google.com>
Date: Mon, 24 Nov 2025 11:04:37 +0000
From: Mostafa Saleh <smostafa@...gle.com>
To: Randy Dunlap <rdunlap@...radead.org>
Cc: linux-mm@...ck.org, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, 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

On Thu, Nov 06, 2025 at 11:50:11AM -0800, Randy Dunlap wrote:
> 
> 
> > 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

I will fix it.

Thanks,
Mostafa

> 
> > +	  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
>