linux-kernel - [PATCH v1 03/11] x86/mm/pat: introduce pfnmap_track() and pfnmap

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Message-ID: <20250425081715.1341199-4-david@redhat.com>
Date: Fri, 25 Apr 2025 10:17:07 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	x86@...nel.org,
	intel-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-trace-kernel@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Jann Horn <jannh@...gle.com>,
	Pedro Falcato <pfalcato@...e.de>,
	Peter Xu <peterx@...hat.com>
Subject: [PATCH v1 03/11] x86/mm/pat: introduce pfnmap_track() and pfnmap_untrack()

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@...hat.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