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") Cc: stable@vger.kernel.org Signed-off-by: David Hildenbrand david@redhat.com
mm/huge_memory.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d3e66136e41a3..49b98082c5401 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1516,10 +1516,9 @@ static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) } static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
pud_t *pud, pfn_t pfn, bool write)
pud_t *pud, pfn_t pfn, pgprot_t prot, bool write){ struct mm_struct *mm = vma->vm_mm;
- pgprot_t prot = vma->vm_page_prot; pud_t entry;
if (!pud_none(*pud)) { @@ -1581,7 +1580,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write) pfnmap_setup_cachemode_pfn(pfn_t_to_pfn(pfn), &pgprot); ptl = pud_lock(vma->vm_mm, vmf->pud);
- insert_pfn_pud(vma, addr, vmf->pud, pfn, write);
- insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write); spin_unlock(ptl);
return VM_FAULT_NOPAGE; @@ -1625,7 +1624,7 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio, add_mm_counter(mm, mm_counter_file(folio), HPAGE_PUD_NR); } insert_pfn_pud(vma, addr, vmf->pud, pfn_to_pfn_t(folio_pfn(folio)),
write);
vma->vm_page_prot, write);
Actually It's not immediately obvious to me why we don't call track_pfn_insert() and forward the pgprot here as well. Prior to me adding vmf_insert_folio_pud() device DAX would call vmf_insert_pfn_pud(), and the intent at least seems to have been to change pgprot for that (and we did for the PTE/PMD versions).
However now that the ZONE_DEVICE folios are refcounted normally I switched device dax to using vmf_insert_folio_*() which never changes pgprot based on x86 PAT. So I think we probably need to either add that to vmf_insert_folio_*() or a new variant or make it the responsibility of callers to figure out the correct pgprot.
spin_unlock(ptl); return VM_FAULT_NOPAGE; -- 2.49.0