linux-kernel - Re: [PATCH v3 1/3] mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn

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Message-ID: <aEwo9aUZTwW_rFJ9@localhost.localdomain>
Date: Fri, 13 Jun 2025 15:34:45 +0200
From: Oscar Salvador <osalvador@...e.de>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alistair Popple <apopple@...dia.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, Zi Yan <ziy@...dia.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
	Dev Jain <dev.jain@....com>,
	Dan Williams <dan.j.williams@...el.com>,
	Jason Gunthorpe <jgg@...dia.com>, stable@...r.kernel.org
Subject: Re: [PATCH v3 1/3] mm/huge_memory: don't ignore queried cachemode in
 vmf_insert_pfn_pud()

On Fri, Jun 13, 2025 at 11:27:00AM +0200, David Hildenbrand wrote:
> We setup the cache mode but ... don't forward the updated pgprot to
> insert_pfn_pud().
> 
> Only a problem on x86-64 PAT when mapping PFNs using PUDs that
> require a special cachemode.
> 
> Fix it by using the proper pgprot where the cachemode was setup.
> 
> It is unclear in which configurations we would get the cachemode wrong:
> through vfio seems possible. Getting cachemodes wrong is usually ... bad.
> As the fix is easy, let's backport it to stable.
> 
> Identified by code inspection.
> 
> Fixes: 7b806d229ef1 ("mm: remove vmf_insert_pfn_xxx_prot() for huge page-table entries")
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> Tested-by: Dan Williams <dan.j.williams@...el.com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Oscar Salvador <osalvador@...e.de>


-- 
Oscar Salvador
SUSE Labs