[PATCH v1 03/11] x86/mm/pat: introduce pfnmap_track() and pfnmap_untrack()

David Hildenbrand
2025-04-25T08:17:33Z

Let's provide variants of track_pfn_remap() and untrack_pfn() that won't
mess with VMAs, to replace the existing interface step-by-step.

Add some documentation.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/x86/mm/pat/memtype.c | 14 ++++++++++++++
include/linux/pgtable.h | 33 +++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index 193e33251b18f..c011d8dd8f441 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -1068,6 +1068,20 @@ int pfnmap_sanitize_pgprot(unsigned long pfn, unsigned long size, pgprot_t *prot
return 0;
}

+int pfnmap_track(unsigned long pfn, unsigned long size, pgprot_t *prot)
+{
+ const resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT;
+
+ return reserve_pfn_range(paddr, size, prot, 0);
+}
+
+void pfnmap_untrack(unsigned long pfn, unsigned long size)
+{
+ const resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT;
+
+ free_pfn_range(paddr, size);
+}
+
/*
* 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
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 91aadfe2515a5..898a3ab195578 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1506,6 +1506,16 @@ static inline int pfnmap_sanitize_pgprot(unsigned long pfn, unsigned long size,
return 0;
}

+static inline int pfnmap_track(unsigned long pfn, unsigned long size,
+ pgprot_t *prot)
+{
+ return 0;
+}
+
+static inline void pfnmap_untrack(unsigned long pfn, unsigned long size)
+{
+}
+
/*
* track_pfn_copy is called when a VM_PFNMAP VMA is about to get the page
* tables copied during copy_page_range(). Will store the pfn to be
@@ -1570,6 +1580,29 @@ extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
*/
int pfnmap_sanitize_pgprot(unsigned long pfn, unsigned long size,
pgprot_t *prot);
+
+/**
+ * pfnmap_track - track a pfn range
+ * @pfn: the start of the pfn range
+ * @size: the size of the pfn range
+ * @prot: the pgprot to track
+ *
+ * Tracking a pfnmap range involves conditionally reserving a pfn range and
+ * sanitizing the pgprot -- see pfnmap_sanitize_pgprot().
+ *
+ * Returns 0 on success and -EINVAL on error.
+ */
+int pfnmap_track(unsigned long pfn, unsigned long size, pgprot_t *prot);
+
+/**
+ * pfnmap_untrack - untrack a pfn range
+ * @pfn: the start of the pfn range
+ * @size: the size of the pfn range
+ *
+ * Untrack a pfn range previously tracked through pfnmap_track(), for example,
+ * un-doing any reservation.
+ */
+void pfnmap_untrack(unsigned long pfn, unsigned long size);
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,
--
2.49.0