+ mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: convert track_pfn_insert() to pfnmap_setup_cachemode*()
has been added to the -mm mm-new branch.  Its filename is
     mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm: convert track_pfn_insert() to pfnmap_setup_cachemode*()
Date: Mon, 12 May 2025 14:34:15 +0200

...  by factoring it out from track_pfn_remap() into
pfnmap_setup_cachemode() and provide pfnmap_setup_cachemode_pfn() as a
replacement for track_pfn_insert().

For PMDs/PUDs, we keep checking a single pfn only.  Add some
documentation, and also document why it is valid to not check the whole
pfn range.

We'll reuse pfnmap_setup_cachemode() from core MM next.

Link: https://lkml.kernel.org/r/20250512123424.637989-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org> # x86 bits
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Airlie <airlied@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/mm/pat/memtype.c |   24 +++++-----------
 include/linux/pgtable.h   |   52 ++++++++++++++++++++++++++++++------
 mm/huge_memory.c          |    5 ++-
 mm/memory.c               |    4 +-
 4 files changed, 57 insertions(+), 28 deletions(-)

--- a/arch/x86/mm/pat/memtype.c~mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode
+++ a/arch/x86/mm/pat/memtype.c
@@ -1031,7 +1031,6 @@ int track_pfn_remap(struct vm_area_struc
 		    unsigned long pfn, unsigned long addr, unsigned long size)
 {
 	resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT;
-	enum page_cache_mode pcm;
 
 	/* reserve the whole chunk starting from paddr */
 	if (!vma || (addr == vma->vm_start
@@ -1044,13 +1043,17 @@ int track_pfn_remap(struct vm_area_struc
 		return ret;
 	}
 
+	return pfnmap_setup_cachemode(pfn, size, prot);
+}
+
+int pfnmap_setup_cachemode(unsigned long pfn, unsigned long size, pgprot_t *prot)
+{
+	resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT;
+	enum page_cache_mode pcm;
+
 	if (!pat_enabled())
 		return 0;
 
-	/*
-	 * For anything smaller than the vma size we set prot based on the
-	 * lookup.
-	 */
 	pcm = lookup_memtype(paddr);
 
 	/* Check memtype for the remaining pages */
@@ -1065,17 +1068,6 @@ int track_pfn_remap(struct vm_area_struc
 	return 0;
 }
 
-void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, pfn_t pfn)
-{
-	enum page_cache_mode pcm;
-
-	if (!pat_enabled())
-		return;
-
-	pcm = lookup_memtype(pfn_t_to_phys(pfn));
-	pgprot_set_cachemode(prot, pcm);
-}
-
 /*
  * untrack_pfn is called while unmapping a pfnmap for a region.
  * untrack can be called for a specific region indicated by pfn and size or
--- a/include/linux/pgtable.h~mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode
+++ a/include/linux/pgtable.h
@@ -1496,13 +1496,10 @@ static inline int track_pfn_remap(struct
 	return 0;
 }
 
-/*
- * track_pfn_insert is called when a _new_ single pfn is established
- * by vmf_insert_pfn().
- */
-static inline void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
-				    pfn_t pfn)
+static inline int pfnmap_setup_cachemode(unsigned long pfn, unsigned long size,
+		pgprot_t *prot)
 {
+	return 0;
 }
 
 /*
@@ -1552,8 +1549,32 @@ static inline void untrack_pfn_clear(str
 extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 			   unsigned long pfn, unsigned long addr,
 			   unsigned long size);
-extern void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
-			     pfn_t pfn);
+
+/**
+ * pfnmap_setup_cachemode - setup the cachemode in the pgprot for a pfn range
+ * @pfn: the start of the pfn range
+ * @size: the size of the pfn range in bytes
+ * @prot: the pgprot to modify
+ *
+ * Lookup the cachemode for the pfn range starting at @pfn with the size
+ * @size and store it in @prot, leaving other data in @prot unchanged.
+ *
+ * This allows for a hardware implementation to have fine-grained control of
+ * memory cache behavior at page level granularity. Without a hardware
+ * implementation, this function does nothing.
+ *
+ * Currently there is only one implementation for this - x86 Page Attribute
+ * Table (PAT). See Documentation/arch/x86/pat.rst for more details.
+ *
+ * This function can fail if the pfn range spans pfns that require differing
+ * cachemodes. If the pfn range was previously verified to have a single
+ * cachemode, it is sufficient to query only a single pfn. The assumption is
+ * that this is the case for drivers using the vmf_insert_pfn*() interface.
+ *
+ * Returns 0 on success and -EINVAL on error.
+ */
+int pfnmap_setup_cachemode(unsigned long pfn, unsigned long size,
+		pgprot_t *prot);
 extern int track_pfn_copy(struct vm_area_struct *dst_vma,
 		struct vm_area_struct *src_vma, unsigned long *pfn);
 extern void untrack_pfn_copy(struct vm_area_struct *dst_vma,
@@ -1563,6 +1584,21 @@ extern void untrack_pfn(struct vm_area_s
 extern void untrack_pfn_clear(struct vm_area_struct *vma);
 #endif
 
+/**
+ * pfnmap_setup_cachemode_pfn - setup the cachemode in the pgprot for a pfn
+ * @pfn: the pfn
+ * @prot: the pgprot to modify
+ *
+ * Lookup the cachemode for @pfn and store it in @prot, leaving other
+ * data in @prot unchanged.
+ *
+ * See pfnmap_setup_cachemode() for details.
+ */
+static inline void pfnmap_setup_cachemode_pfn(unsigned long pfn, pgprot_t *prot)
+{
+	pfnmap_setup_cachemode(pfn, PAGE_SIZE, prot);
+}
+
 #ifdef CONFIG_MMU
 #ifdef __HAVE_COLOR_ZERO_PAGE
 static inline int is_zero_pfn(unsigned long pfn)
--- a/mm/huge_memory.c~mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode
+++ a/mm/huge_memory.c
@@ -1455,7 +1455,8 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_
 			return VM_FAULT_OOM;
 	}
 
-	track_pfn_insert(vma, &pgprot, pfn);
+	pfnmap_setup_cachemode_pfn(pfn_t_to_pfn(pfn), &pgprot);
+
 	ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 	error = insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write,
 			pgtable);
@@ -1577,7 +1578,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_
 	if (addr < vma->vm_start || addr >= vma->vm_end)
 		return VM_FAULT_SIGBUS;
 
-	track_pfn_insert(vma, &pgprot, pfn);
+	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);
--- a/mm/memory.c~mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode
+++ a/mm/memory.c
@@ -2564,7 +2564,7 @@ vm_fault_t vmf_insert_pfn_prot(struct vm
 	if (!pfn_modify_allowed(pfn, pgprot))
 		return VM_FAULT_SIGBUS;
 
-	track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
+	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
 
 	return insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
 			false);
@@ -2627,7 +2627,7 @@ static vm_fault_t __vm_insert_mixed(stru
 	if (addr < vma->vm_start || addr >= vma->vm_end)
 		return VM_FAULT_SIGBUS;
 
-	track_pfn_insert(vma, &pgprot, pfn);
+	pfnmap_setup_cachemode_pfn(pfn_t_to_pfn(pfn), &pgprot);
 
 	if (!pfn_modify_allowed(pfn_t_to_pfn(pfn), pgprot))
 		return VM_FAULT_SIGBUS;
_

Patches currently in -mm which might be from david@redhat.com are

selftests-mm-add-simple-vm_pfnmap-tests-based-on-mmaping-dev-mem.patch
x86-mm-pat-factor-out-setting-cachemode-into-pgprot_set_cachemode.patch
mm-convert-track_pfn_insert-to-pfnmap_setup_cachemode.patch
mm-introduce-pfnmap_track-and-pfnmap_untrack-and-use-them-for-memremap.patch
mm-convert-vm_pfnmap-tracking-to-pfnmap_track-pfnmap_untrack.patch
x86-mm-pat-remove-old-pfnmap-tracking-interface.patch
mm-remove-vm_pat.patch
x86-mm-pat-remove-strict_prot-parameter-from-reserve_pfn_range.patch
x86-mm-pat-remove-memtype__match.patch
x86-mm-pat-inline-memtype_match-into-memtype_erase.patch
drm-i915-track_pfn-pfnmap-tracking.patch
mm-io-mapping-track_pfn-pfnmap-tracking.patch