Re: [PATCH v2 1/3] mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn_pud()

[David Hildenbrand <david@redhat.com>]

On 12.06.25 17:59, Lorenzo Stoakes wrote:
> On Thu, Jun 12, 2025 at 05:36:35PM +0200, David Hildenbrand wrote:
>> On 12.06.25 17:28, Lorenzo Stoakes wrote:
>>> On Wed, Jun 11, 2025 at 02:06:52PM +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.
>>>>
>>>> Identified by code inspection.
>>>>
>>>> Fixes: 7b806d229ef1 ("mm: remove vmf_insert_pfn_xxx_prot() for huge page-table entries")
> 
> Ha! I don't even remember doing that patch... hm did I introduce this -ignoring
> cache- thing? Sorry! :P

:)

> 
>>>> Cc: <stable@vger.kernel.org>
>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>
>>> Nice catch!
>>>
>>> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>>
>> Thanks! What's your opinion on stable? Really hard to judge the impact ...
> 
> I think it makes sense? This is currently incorrect so let's do the right thing
> and backport.
> 
> I think as per Dan it's probably difficult to picture this causing a problem,
> but on principle I think this is correct, and I don't see any harm in
> backporting?

Same opinion, thanks!

-- 
Cheers,

David / dhildenb