[PATCH v5 0/4] Convert 64-bit x86/mm/pat to ptdescs

[PATCH v5 0/4] Convert 64-bit x86/mm/pat to ptdescs

[Vishal Moola (Oracle)]

x86/mm/pat should be using ptdescs. One line has already been
converted to pagetable_free(), while the allocation sites use
get_free_pages(). This causes issues separately allocating ptdescs
from struct page.

The first patch introduces new ptdesc apis that operate on addresses.
These are like get_free_pages() and free_pages() helper functions.

The remaining patches convert the allocation/free sites to use ptdescs. In
the short term, this helps enable Matthew's work to allocate frozen
pagetables[1]. And in the long term, this will help us cleanly split
ptdesc allocations from struct page[2].

The pgd_list should also be using ptdescs (for 32bit in this file). This
can be done in a different patchset since there's other users of pgd_list
that still need to be converted.

[1] https://lore.kernel.org/linux-mm/20251113140448.1814860-1-willy@infradead.org/
[2] https://lore.kernel.org/linux-mm/20251020001652.2116669-1-willy@infradead.org/

------

Based on current mm-new.

v5:
  - Return a void pointer instead of unsigned long in allocation
  - More imperative voice in commit logs

Vishal Moola (Oracle) (4):
  mm: Add address apis for ptdescs
  x86/mm/pat: Convert pte code to use ptdescs
  x86/mm/pat: Convert pmd code to use ptdescs
  x86/mm/pat: Convert split_large_page() to use ptdescs

 arch/x86/mm/pat/set_memory.c | 49 ++++++++++++++++++------------------
 include/linux/mm.h           |  4 +++
 mm/memory.c                  | 34 +++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 24 deletions(-)

-- 
2.52.0

[PATCH v5 1/4] mm: Add address apis for ptdescs

[Vishal Moola (Oracle)]

Architectures frequently only care about the address associated with a
page table. The current ptdesc api forced callers to acquire a ptdesc to
use them. Add more apis to abstract ptdescs away from architectures that
don't need the descriptor.

Add pgtable_alloc_addr() and pgtable_free_addr() to operate on the
underlying addresses associated with page table descriptors, similar to
get_free_pages() and free_pages(). Zero the allocations since
theres no reason to want a page table with stale data.

Have pgtable_alloc_addr() return a void pointer. This will simplify code
for callers since they all want pointers.

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 include/linux/mm.h |  4 ++++
 mm/memory.c        | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f8a8fd47399c..9b6d3d910990 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3419,6 +3419,10 @@ static inline void __pagetable_free(struct ptdesc *pt)
 	__free_pages(page, compound_order(page));
 }
 
+void *pgtable_alloc_addr_noprof(gfp_t gfp, unsigned int order);
+#define pgtable_alloc_addr(...)     alloc_hooks(pgtable_alloc_addr_noprof(__VA_ARGS__))
+void pgtable_free_addr(const void *addr);
+
 #ifdef CONFIG_ASYNC_KERNEL_PGTABLE_FREE
 void pagetable_free_kernel(struct ptdesc *pt);
 #else
diff --git a/mm/memory.c b/mm/memory.c
index 1a26947ed8cd..b9653377d647 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -7452,6 +7452,40 @@ long copy_folio_from_user(struct folio *dst_folio,
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
 
+/**
+ * pgtable_alloc_addr - Allocate pagetables to get an address
+ * @gfp:       GFP flags
+ * @order:     desired pagetable order
+ *
+ * pgtable_alloc_addr is like pagetable_alloc. This is for callers who only want a
+ * page table's address, not its ptdesc.
+ *
+ * Return: The address associated with the allocated page table, or 0 on
+ * failure.
+ */
+void *pgtable_alloc_addr_noprof(gfp_t gfp, unsigned int order)
+{
+	struct ptdesc *ptdesc = pagetable_alloc_noprof(gfp | __GFP_ZERO, order);
+
+	if (!ptdesc)
+		return 0;
+	return ptdesc_address(ptdesc);
+}
+
+/**
+ * pgtable_free_addr - Free pagetables by address
+ * @addr:      The virtual address from pgtable_alloc()
+ *
+ * This function is for callers who have the address but no ptdesc. If you
+ * have the ptdesc, use pagetable_free() instead.
+ */
+void pgtable_free_addr(const void *addr)
+{
+	struct ptdesc *ptdesc = virt_to_ptdesc(addr);
+
+	pagetable_free(ptdesc);
+}
+
 #if defined(CONFIG_SPLIT_PTE_PTLOCKS) && ALLOC_SPLIT_PTLOCKS
 
 static struct kmem_cache *page_ptl_cachep;
-- 
2.52.0

Re: [PATCH v5 1/4] mm: Add address apis for ptdescs

[Dave Hansen]

On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> +/**
> + * pgtable_alloc_addr - Allocate pagetables to get an address
> + * @gfp:       GFP flags
> + * @order:     desired pagetable order

FWIW, I don't like how pgtable_alloc_addr() looks in practice. It reads
like it is: "allocate a page table address", not "allocate a page
table". I don't have a better suggestion other than having:

	pgtable_alloc()

that returns a page table pointer, a void*, and:

	ptdesc_alloc()

which returns a ptdesc*. But I suspect that would get confusing at the
point that ptdescs _themselves_ start getting allocated.

Re: [PATCH v5 1/4] mm: Add address apis for ptdescs

[Matthew Wilcox]

On Wed, Feb 11, 2026 at 12:13:10PM -0800, Dave Hansen wrote:
> On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> > +/**
> > + * pgtable_alloc_addr - Allocate pagetables to get an address
> > + * @gfp:       GFP flags
> > + * @order:     desired pagetable order
> 
> FWIW, I don't like how pgtable_alloc_addr() looks in practice. It reads
> like it is: "allocate a page table address", not "allocate a page
> table". I don't have a better suggestion other than having:
> 
> 	pgtable_alloc()
> 
> that returns a page table pointer, a void*, and:
> 
> 	ptdesc_alloc()
> 
> which returns a ptdesc*. But I suspect that would get confusing at the
> point that ptdescs _themselves_ start getting allocated.

I think that's fine and consistent with folio_alloc().  Internally to
ptdesc_alloc(), it'll use a kmem_cache_alloc(), so there won't be
any confusion.

Re: [PATCH v5 1/4] mm: Add address apis for ptdescs

[Vishal Moola (Oracle)]

On Wed, Feb 11, 2026 at 12:13:10PM -0800, Dave Hansen wrote:
> On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> > +/**
> > + * pgtable_alloc_addr - Allocate pagetables to get an address
> > + * @gfp:       GFP flags
> > + * @order:     desired pagetable order
> 
> FWIW, I don't like how pgtable_alloc_addr() looks in practice. It reads
> like it is: "allocate a page table address", not "allocate a page
> table". I don't have a better suggestion other than having:

Hmmm. I meant for it to read "allocate a page table and get its address."

> 	pgtable_alloc()
> 
> that returns a page table pointer, a void*, and:

Initially, I intended to name it pgtable_alloc() & pgtable_free(). I saw
arm using pgtable_alloc() and powerpc using pgtable_free(), so I looked
for another name.

> 	ptdesc_alloc()
> 
> which returns a ptdesc*. But I suspect that would get confusing at the
> point that ptdescs _themselves_ start getting allocated.

The ptdesc_alloc() equivalent right now is named pagetable_alloc(), so I
don't think it'd get confusing.

Re: [PATCH v5 1/4] mm: Add address apis for ptdescs

[Vishal Moola (Oracle)]

On Wed, Feb 11, 2026 at 02:18:20PM -0800, Vishal Moola (Oracle) wrote:
> On Wed, Feb 11, 2026 at 12:13:10PM -0800, Dave Hansen wrote:
> > On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> > > +/**
> > > + * pgtable_alloc_addr - Allocate pagetables to get an address
> > > + * @gfp:       GFP flags
> > > + * @order:     desired pagetable order
> > 
> > FWIW, I don't like how pgtable_alloc_addr() looks in practice. It reads
> > like it is: "allocate a page table address", not "allocate a page
> > table". I don't have a better suggestion other than having:
> 
> Hmmm. I meant for it to read "allocate a page table and get its address."
> 
> > 	pgtable_alloc()
> > 
> > that returns a page table pointer, a void*, and:
> 
> Initially, I intended to name it pgtable_alloc() & pgtable_free(). I saw
> arm using pgtable_alloc() and powerpc using pgtable_free(), so I looked
> for another name.

I've done some digging about these names.
The arm cases uses a function pointer, so we should be able to use that
name without issue.

What do you think is a reasonable name for freeing?

pgtable_free() is defined for sparc and powerpc. I could rename them
prefixed with "__" to get the name since they only have 1-2 internal
callers.

> > 	ptdesc_alloc()
> > 
> > which returns a ptdesc*. But I suspect that would get confusing at the
> > point that ptdescs _themselves_ start getting allocated.
> 
> The ptdesc_alloc() equivalent right now is named pagetable_alloc(), so I
> don't think it'd get confusing.

Re: [PATCH v5 1/4] mm: Add address apis for ptdescs

[Vishal Moola (Oracle)]

On Wed, Feb 11, 2026 at 04:07:54PM -0800, Vishal Moola (Oracle) wrote:
> On Wed, Feb 11, 2026 at 02:18:20PM -0800, Vishal Moola (Oracle) wrote:
> > On Wed, Feb 11, 2026 at 12:13:10PM -0800, Dave Hansen wrote:
> > > On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> > > > +/**
> > > > + * pgtable_alloc_addr - Allocate pagetables to get an address
> > > > + * @gfp:       GFP flags
> > > > + * @order:     desired pagetable order
> > > 
> > > FWIW, I don't like how pgtable_alloc_addr() looks in practice. It reads
> > > like it is: "allocate a page table address", not "allocate a page
> > > table". I don't have a better suggestion other than having:
> > 
> > Hmmm. I meant for it to read "allocate a page table and get its address."
> > 
> > > 	pgtable_alloc()
> > > 
> > > that returns a page table pointer, a void*, and:
> > 
> > Initially, I intended to name it pgtable_alloc() & pgtable_free(). I saw
> > arm using pgtable_alloc() and powerpc using pgtable_free(), so I looked
> > for another name.
> 
> I've done some digging about these names.
> The arm cases uses a function pointer, so we should be able to use that
> name without issue.

Dave, I wanted to follow up on the below question:

> What do you think is a reasonable name for freeing?
>
> pgtable_free() is defined for sparc and powerpc. I could rename them
> prefixed with "__" to get the name since they only have 1-2 internal
> callers.

Matthew brought another question to my attention in this particular
scenario. Should pat/set_memory's alloc_*_page() use pte_alloc_one()
instead of get_zeroed_page()? Is there any reason not to?

Re: [PATCH v5 1/4] mm: Add address apis for ptdescs

[Dave Hansen]

On 2/18/26 12:23, Vishal Moola (Oracle) wrote:
>> What do you think is a reasonable name for freeing?
>>
>> pgtable_free() is defined for sparc and powerpc. I could rename them
>> prefixed with "__" to get the name since they only have 1-2 internal
>> callers.
> Matthew brought another question to my attention in this particular
> scenario. Should pat/set_memory's alloc_*_page() use pte_alloc_one()
> instead of get_zeroed_page()? Is there any reason not to?

They're not special in any way I can think of. There's no reason I know
of to keep them special and avoid converting them.

[PATCH v5 2/4] x86/mm/pat: Convert pte code to use ptdescs

[Vishal Moola (Oracle)]

We need all allocation and free sites to use the ptdesc APIs in order to
allocate them separately from regular pages. Convert these pte
allocation/free sites to use ptdescs.

Also, rename *_pte_page() functions to *_pte(). Rename them now to avoid
any confusion later. Eventually these allocations will be backed by a
ptdesc not a page, but that's not important to callers either.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/x86/mm/pat/set_memory.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 6c6eb486f7a6..04eae65aedfc 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1400,7 +1400,7 @@ static int collapse_large_pages(unsigned long addr, struct list_head *pgtables)
 	return collapsed;
 }
 
-static bool try_to_free_pte_page(pte_t *pte)
+static bool try_to_free_pte(pte_t *pte)
 {
 	int i;
 
@@ -1408,7 +1408,7 @@ static bool try_to_free_pte_page(pte_t *pte)
 		if (!pte_none(pte[i]))
 			return false;
 
-	free_page((unsigned long)pte);
+	pgtable_free_addr(pte);
 	return true;
 }
 
@@ -1435,7 +1435,7 @@ static bool unmap_pte_range(pmd_t *pmd, unsigned long start, unsigned long end)
 		pte++;
 	}
 
-	if (try_to_free_pte_page((pte_t *)pmd_page_vaddr(*pmd))) {
+	if (try_to_free_pte((pte_t *)pmd_page_vaddr(*pmd))) {
 		pmd_clear(pmd);
 		return true;
 	}
@@ -1537,9 +1537,9 @@ static void unmap_pud_range(p4d_t *p4d, unsigned long start, unsigned long end)
 	 */
 }
 
-static int alloc_pte_page(pmd_t *pmd)
+static int alloc_pte(pmd_t *pmd)
 {
-	pte_t *pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
+	pte_t *pte = pgtable_alloc_addr(GFP_KERNEL, 0);
 	if (!pte)
 		return -1;
 
@@ -1600,7 +1600,7 @@ static long populate_pmd(struct cpa_data *cpa,
 		 */
 		pmd = pmd_offset(pud, start);
 		if (pmd_none(*pmd))
-			if (alloc_pte_page(pmd))
+			if (alloc_pte(pmd))
 				return -1;
 
 		populate_pte(cpa, start, pre_end, cur_pages, pmd, pgprot);
@@ -1641,7 +1641,7 @@ static long populate_pmd(struct cpa_data *cpa,
 	if (start < end) {
 		pmd = pmd_offset(pud, start);
 		if (pmd_none(*pmd))
-			if (alloc_pte_page(pmd))
+			if (alloc_pte(pmd))
 				return -1;
 
 		populate_pte(cpa, start, end, num_pages - cur_pages,
-- 
2.52.0

Re: [PATCH v5 2/4] x86/mm/pat: Convert pte code to use ptdescs

[Matthew Wilcox]

On Wed, Feb 11, 2026 at 11:52:31AM -0800, Vishal Moola (Oracle) wrote:
> -static bool try_to_free_pte_page(pte_t *pte)
> +static bool try_to_free_pte(pte_t *pte)

I don't like this name though.  You're not freeing a single PTE,
you're freeing a level of page tables.  How about
try_to_free_pte_table()?

Re: [PATCH v5 2/4] x86/mm/pat: Convert pte code to use ptdescs

[Vishal Moola (Oracle)]

On Wed, Feb 11, 2026 at 09:55:51PM +0000, Matthew Wilcox wrote:
> On Wed, Feb 11, 2026 at 11:52:31AM -0800, Vishal Moola (Oracle) wrote:
> > -static bool try_to_free_pte_page(pte_t *pte)
> > +static bool try_to_free_pte(pte_t *pte)
> 
> I don't like this name though.  You're not freeing a single PTE,
> you're freeing a level of page tables.  How about
> try_to_free_pte_table()?

Ah, right. That would make sense to me.

Dave doesn't want the renaming at all[1], so I'm planning to leave it as
try_to_free_pte_page() though.

[1] https://lore.kernel.org/linux-mm/20260211195233.368497-1-vishal.moola@gmail.com/T/#m72f1d8d91b16f0693cca4271cc8685d2337372d7

Re: [PATCH v5 2/4] x86/mm/pat: Convert pte code to use ptdescs

[Dave Hansen]

On 2/11/26 14:23, Vishal Moola (Oracle) wrote:
> On Wed, Feb 11, 2026 at 09:55:51PM +0000, Matthew Wilcox wrote:
>> On Wed, Feb 11, 2026 at 11:52:31AM -0800, Vishal Moola (Oracle) wrote:
>>> -static bool try_to_free_pte_page(pte_t *pte)
>>> +static bool try_to_free_pte(pte_t *pte)
>> I don't like this name though.  You're not freeing a single PTE,
>> you're freeing a level of page tables.  How about
>> try_to_free_pte_table()?
> Ah, right. That would make sense to me.
> 
> Dave doesn't want the renaming at all[1], so I'm planning to leave it as
> try_to_free_pte_page() though.

Let's just talk about renaming later, please. I'm not totally against
it, but there is enough going on in this set already.

[PATCH v5 3/4] x86/mm/pat: Convert pmd code to use ptdescs

[Vishal Moola (Oracle)]

We need all allocation and free sites to use the ptdesc APIs in order to
allocate them separately from regular pages. Convert these pmd
allocation/free sites to use ptdescs.

Allocate ptdescs in popoulate_pgd() as well since those allocations may
later be freed by try_to_free_pmd_page().

Also, rename *_pmd_page() functions to *_pmd(). Rename them now to avoid
any confusion later. Eventually these allocations will be backed by a
ptdesc not a page, but that's not important to callers either.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/x86/mm/pat/set_memory.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 04eae65aedfc..9d6681443e54 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1412,7 +1412,7 @@ static bool try_to_free_pte(pte_t *pte)
 	return true;
 }
 
-static bool try_to_free_pmd_page(pmd_t *pmd)
+static bool try_to_free_pmd(pmd_t *pmd)
 {
 	int i;
 
@@ -1420,7 +1420,7 @@ static bool try_to_free_pmd_page(pmd_t *pmd)
 		if (!pmd_none(pmd[i]))
 			return false;
 
-	free_page((unsigned long)pmd);
+	pgtable_free_addr(pmd);
 	return true;
 }
 
@@ -1446,7 +1446,7 @@ static void __unmap_pmd_range(pud_t *pud, pmd_t *pmd,
 			      unsigned long start, unsigned long end)
 {
 	if (unmap_pte_range(pmd, start, end))
-		if (try_to_free_pmd_page(pud_pgtable(*pud)))
+		if (try_to_free_pmd(pud_pgtable(*pud)))
 			pud_clear(pud);
 }
 
@@ -1490,7 +1490,7 @@ static void unmap_pmd_range(pud_t *pud, unsigned long start, unsigned long end)
 	 * Try again to free the PMD page if haven't succeeded above.
 	 */
 	if (!pud_none(*pud))
-		if (try_to_free_pmd_page(pud_pgtable(*pud)))
+		if (try_to_free_pmd(pud_pgtable(*pud)))
 			pud_clear(pud);
 }
 
@@ -1547,9 +1547,9 @@ static int alloc_pte(pmd_t *pmd)
 	return 0;
 }
 
-static int alloc_pmd_page(pud_t *pud)
+static int alloc_pmd(pud_t *pud)
 {
-	pmd_t *pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
+	pmd_t *pmd = pgtable_alloc_addr(GFP_KERNEL, 0);
 	if (!pmd)
 		return -1;
 
@@ -1622,7 +1622,7 @@ static long populate_pmd(struct cpa_data *cpa,
 		 * We cannot use a 1G page so allocate a PMD page if needed.
 		 */
 		if (pud_none(*pud))
-			if (alloc_pmd_page(pud))
+			if (alloc_pmd(pud))
 				return -1;
 
 		pmd = pmd_offset(pud, start);
@@ -1678,7 +1678,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 		 * Need a PMD page?
 		 */
 		if (pud_none(*pud))
-			if (alloc_pmd_page(pud))
+			if (alloc_pmd(pud))
 				return -1;
 
 		cur_pages = populate_pmd(cpa, start, pre_end, cur_pages,
@@ -1715,7 +1715,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 
 		pud = pud_offset(p4d, start);
 		if (pud_none(*pud))
-			if (alloc_pmd_page(pud))
+			if (alloc_pmd(pud))
 				return -1;
 
 		tmp = populate_pmd(cpa, start, end, cpa->numpages - cur_pages,
@@ -1743,7 +1743,7 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	pgd_entry = cpa->pgd + pgd_index(addr);
 
 	if (pgd_none(*pgd_entry)) {
-		p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);
+		p4d = pgtable_alloc_addr(GFP_KERNEL, 0);
 		if (!p4d)
 			return -1;
 
@@ -1755,7 +1755,7 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	 */
 	p4d = p4d_offset(pgd_entry, addr);
 	if (p4d_none(*p4d)) {
-		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
+		pud = pgtable_alloc_addr(GFP_KERNEL, 0);
 		if (!pud)
 			return -1;
 
-- 
2.52.0

Re: [PATCH v5 3/4] x86/mm/pat: Convert pmd code to use ptdescs

[Dave Hansen]

On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> Also, rename *_pmd_page() functions to *_pmd(). Rename them now to avoid
> any confusion later. Eventually these allocations will be backed by a
> ptdesc not a page, but that's not important to callers either.

So, pages are still a thing, whether the API says 'struct page' or not.
The hardware kinda uses pages for page tables. ;)

Could we please leave out the unnecessary churn from the renames?

Re: [PATCH v5 3/4] x86/mm/pat: Convert pmd code to use ptdescs

[Vishal Moola (Oracle)]

On Wed, Feb 11, 2026 at 12:07:05PM -0800, Dave Hansen wrote:
> On 2/11/26 11:52, Vishal Moola (Oracle) wrote:
> > Also, rename *_pmd_page() functions to *_pmd(). Rename them now to avoid
> > any confusion later. Eventually these allocations will be backed by a
> > ptdesc not a page, but that's not important to callers either.
> 
> So, pages are still a thing, whether the API says 'struct page' or not.
> The hardware kinda uses pages for page tables. ;)
>
> Could we please leave out the unnecessary churn from the renames?

Yeah I'll drop the renames. I thought it'd be better for
correctness-sake, as the idea is to "allocate memory for a page table"
rather than "allocate a generic page for a page table."

As long as its using the right APIs the naming doesn't really matter
to me.

[PATCH v5 4/4] x86/mm/pat: Convert split_large_page() to use ptdescs

[Vishal Moola (Oracle)]

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

Re: [PATCH v5 4/4] x86/mm/pat: Convert split_large_page() to use ptdescs

[Matthew Wilcox]

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?

Re: [PATCH v5 4/4] x86/mm/pat: Convert split_large_page() to use ptdescs

[Vishal Moola (Oracle)]

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.