In order to separately allocate ptdescs from pages, we need all allocation
and free sites to use the appropriate functions.

split_large_page() allocates a page to be used as a page table. This
should be allocating a ptdesc, so convert it.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 9d6681443e54..dfaec7b16ac4 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1119,9 +1119,10 @@ static void split_set_pte(struct cpa_data *cpa, pte_t *pte, unsigned long pfn,
 
 static int
 __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
-		   struct page *base)
+		   struct ptdesc *ptdesc)
 {
 	unsigned long lpaddr, lpinc, ref_pfn, pfn, pfninc = 1;
+	struct page *base = ptdesc_page(ptdesc);
 	pte_t *pbase = (pte_t *)page_address(base);
 	unsigned int i, level;
 	pgprot_t ref_prot;
@@ -1226,18 +1227,18 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
 static int split_large_page(struct cpa_data *cpa, pte_t *kpte,
 			    unsigned long address)
 {
-	struct page *base;
+	struct ptdesc *ptdesc;
 
 	if (!debug_pagealloc_enabled())
 		spin_unlock(&cpa_lock);
-	base = alloc_pages(GFP_KERNEL, 0);
+	ptdesc = pagetable_alloc(GFP_KERNEL, 0);
 	if (!debug_pagealloc_enabled())
 		spin_lock(&cpa_lock);
-	if (!base)
+	if (!ptdesc)
 		return -ENOMEM;
 
-	if (__split_large_page(cpa, kpte, address, base))
-		__free_page(base);
+	if (__split_large_page(cpa, kpte, address, ptdesc))
+		pagetable_free(ptdesc);
 
 	return 0;
 }
-- 
2.52.0

On Wed, Feb 11, 2026 at 11:52:33AM -0800, Vishal Moola (Oracle) wrote:
>  static int
>  __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
> -		   struct page *base)
> +		   struct ptdesc *ptdesc)
>  {
>  	unsigned long lpaddr, lpinc, ref_pfn, pfn, pfninc = 1;
> +	struct page *base = ptdesc_page(ptdesc);
>  	pte_t *pbase = (pte_t *)page_address(base);

We have ptdesc_address() already.  Can we avoid the other uses of
'base' in this function?

On Wed, Feb 11, 2026 at 09:59:19PM +0000, Matthew Wilcox wrote:
> On Wed, Feb 11, 2026 at 11:52:33AM -0800, Vishal Moola (Oracle) wrote:
> >  static int
> >  __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
> > -		   struct page *base)
> > +		   struct ptdesc *ptdesc)
> >  {
> >  	unsigned long lpaddr, lpinc, ref_pfn, pfn, pfninc = 1;
> > +	struct page *base = ptdesc_page(ptdesc);
> >  	pte_t *pbase = (pte_t *)page_address(base);
> 
> We have ptdesc_address() already.  Can we avoid the other uses of
> 'base' in this function?

We could, but not without helpers similar to folio_pfn() and
folio_mk_pte(). I hadn't added those in this patchset since my primary
goal right now is to ensure all the allocation/free sites are using the
proper apis.