linux-kernel - Re: [PATCH v6 3/4] iommu: debug-pagealloc: Track IOMMU pages

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Message-ID: <f239e391-ac7c-4d26-ab82-4024a77ec3d3@kernel.org>
Date: Wed, 14 Jan 2026 18:30:24 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>, 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, 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, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com,
 rppt@...nel.org, xiaqinxin@...wei.com, baolu.lu@...ux.intel.com,
 rdunlap@...radead.org, Samiullah Khawaja <skhawaja@...gle.com>
Subject: Re: [PATCH v6 3/4] iommu: debug-pagealloc: Track IOMMU pages

On 1/13/26 16:08, Jason Gunthorpe wrote:
> On Tue, Jan 13, 2026 at 10:49:28AM +0000, Mostafa Saleh wrote:
>> Would you have a problem if we added a new function in page_ext
>> "page_ext_from_phys()" as Jason suggested?
> 
> Given the hidden complexity that David just pointed out I think this
> is essential to encapsulate it in a function.
> 
> The function must be able to accept any phys_addr_t and safely returns
> NULL if page_ext cannot be used for some reason.

Right. I think pfn_to_online_page() is the appropriate check.

@Mostafa, I saw you already sent a v7, is the pfn_to_online_page() stuff 
handled in there?

-- 
Cheers

David