linux-kernel - [RFC 1/2] mm/mthp: add pte_range_none_or

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250120012230.3343-2-ioworker0@gmail.com>
Date: Mon, 20 Jan 2025 09:22:29 +0800
From: Lance Yang <ioworker0@...il.com>
To: akpm@...ux-foundation.org
Cc: 21cnbao@...il.com,
	ryan.roberts@....com,
	dev.jain@....com,
	david@...hat.com,
	shy828301@...il.com,
	ziy@...dia.com,
	libang.li@...group.com,
	baolin.wang@...ux.alibaba.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Lance Yang <ioworker0@...il.com>,
	Mingzhe Yang <mingzhe.yang@...com>
Subject: [RFC 1/2] mm/mthp: add pte_range_none_or_zeropfn() helper

In preparation for relaxing the mTHP PTE mapping restriction on the demand
zero page. We intend to provide more opportunities to take advantage of
mTHP.

Signed-off-by: Mingzhe Yang <mingzhe.yang@...com>
Signed-off-by: Lance Yang <ioworker0@...il.com>
---
 mm/memory.c | 43 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 2a20e3810534..4e148309b3e0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4724,18 +4724,55 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	return ret;
 }
 
-static bool pte_range_none(pte_t *pte, int nr_pages)
+/* Flags for __pte_range_check(). */
+typedef int __bitwise prc_t;
+
+/* Check if PTEs are not present. */
+#define PRC_CHECK_NONE ((__force prc_t)BIT(0))
+
+/* Check if PTEs are mapped to the zero page. */
+#define PRC_CHECK_ZEROPFN ((__force prc_t)BIT(1))
+
+static bool __pte_range_check(pte_t *pte, int nr_pages, prc_t flags,
+			      bool *any_zeropfn)
 {
 	int i;
+	pte_t ptent;
+
+	if (any_zeropfn)
+		*any_zeropfn = false;
 
 	for (i = 0; i < nr_pages; i++) {
-		if (!pte_none(ptep_get_lockless(pte + i)))
-			return false;
+		ptent = ptep_get_lockless(pte + i);
+
+		if ((flags & PRC_CHECK_NONE) && pte_none(ptent))
+			continue;
+
+		if ((flags & PRC_CHECK_ZEROPFN) &&
+		    is_zero_pfn(pte_pfn(ptent))) {
+			if (any_zeropfn)
+				*any_zeropfn = true;
+			continue;
+		}
+
+		return false;
 	}
 
 	return true;
 }
 
+static inline bool pte_range_none(pte_t *pte, int nr_pages)
+{
+	return __pte_range_check(pte, nr_pages, PRC_CHECK_NONE, NULL);
+}
+
+static inline bool pte_range_none_or_zeropfn(pte_t *pte, int nr_pages,
+					     bool *any_zeropfn)
+{
+	return __pte_range_check(
+		pte, nr_pages, PRC_CHECK_NONE | PRC_CHECK_ZEROPFN, any_zeropfn);
+}
+
 static struct folio *alloc_anon_folio(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
-- 
2.45.2