[to-be-updated] string-introduce-memcpy_nt-helpers.patch removed from -mm tree

[to-be-updated] string-introduce-memcpy_nt-helpers.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: string: introduce memcpy_nt() helpers
has been removed from the -mm tree.  Its filename was
     string-introduce-memcpy_nt-helpers.patch

This patch was dropped because an updated version will be issued

------------------------------------------------------
From: "Li Zhe" <lizhe.67@bytedance.com>
Subject: string: introduce memcpy_nt() helpers
Date: Wed, 1 Jul 2026 17:05:51 +0800

Introduce memcpy_nt() and memcpy_nt_drain() for write-once copy sites that
want a named non-temporal copy primitive plus an explicit ordering point. 
On x86, place the arch-visible wrapper in arch/x86/include/asm/string_64.h
and map it to the existing memcpy_flushcache() backend plus sfence. 
Architectures that do not override the helper fall back to memcpy() and a
no-op drain in include/linux/string.h.

The immediate user is the ZONE_DEVICE template-copy path.  That path
populates struct page descriptors in a write-once pattern, so most
destination cachelines are not expected to be reused immediately after the
copy.  A regular cached memcpy() can therefore incur avoidable
write-allocate traffic and pollute the cache with data that has little
near-term reuse.

This interface lets callers request that non-temporal-copy semantics
directly, while x86 simply reuses the existing memcpy_flushcache() backend
instead of adding another generic memcpy-like wrapper with extra selection
policy above it.

Link: https://lore.kernel.org/20260701090553.62691-7-lizhe.67@bytedance.com
Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/include/asm/string_64.h |   16 ++++++++++++++++
 include/linux/string.h           |   18 ++++++++++++++++++
 2 files changed, 34 insertions(+)

--- a/arch/x86/include/asm/string_64.h~string-introduce-memcpy_nt-helpers
+++ a/arch/x86/include/asm/string_64.h
@@ -100,6 +100,22 @@ static __always_inline void memcpy_flush
 	}
 	__memcpy_flushcache(dst, src, cnt);
 }
+
+#define __HAVE_ARCH_MEMCPY_NT 1
+/*
+ * Reuse the existing x86 flushcache backend as the nt copy primitive.
+ * Callers pair it with memcpy_nt_drain() when later stores must be
+ * ordered after the copy.
+ */
+static __always_inline void memcpy_nt(void *dst, const void *src, size_t cnt)
+{
+	memcpy_flushcache(dst, src, cnt);
+}
+
+static __always_inline void memcpy_nt_drain(void)
+{
+	asm volatile("sfence" : : : "memory");
+}
 #endif
 
 #endif /* __KERNEL__ */
--- a/include/linux/string.h~string-introduce-memcpy_nt-helpers
+++ a/include/linux/string.h
@@ -278,6 +278,24 @@ static inline void memcpy_flushcache(voi
 }
 #endif
 
+#ifndef __HAVE_ARCH_MEMCPY_NT
+/*
+ * memcpy_nt() requests a non-temporal copy when the architecture has a
+ * suitable backend. Callers must follow it with memcpy_nt_drain()
+ * before later normal stores that need to be ordered after the copy.
+ * Architectures that do not override it fall back to memcpy() and a
+ * no-op drain.
+ */
+static inline void memcpy_nt(void *dst, const void *src, size_t cnt)
+{
+	memcpy(dst, src, cnt);
+}
+
+static inline void memcpy_nt_drain(void)
+{
+}
+#endif
+
 void *memchr_inv(const void *s, int c, size_t n);
 char *strreplace(char *str, char old, char new);
 
_

Patches currently in -mm which might be from lizhe.67@bytedance.com are

x86-string-extend-memcpy_flushcache-fixed-size-fastpaths.patch
mm-use-memcpy_nt-in-zone-device-template-copies.patch