netdev - [PATCH 1/6] x86: Stop using weak symbols for __iowrite32

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Date: Tue, 20 Feb 2024 21:17:05 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Leon Romanovsky <leon@...nel.org>,
	linux-rdma@...r.kernel.org,
	linux-s390@...r.kernel.org,
	llvm@...ts.linux.dev,
	Ingo Molnar <mingo@...hat.com>,
	Bill Wendling <morbo@...gle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>,
	Salil Mehta <salil.mehta@...wei.com>,
	Jijie Shao <shaojijie@...wei.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	x86@...nel.org,
	Yisen Zhuang <yisen.zhuang@...wei.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Leon Romanovsky <leonro@...lanox.com>,
	linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Mark Rutland <mark.rutland@....com>,
	Michael Guralnik <michaelgur@...lanox.com>,
	patches@...ts.linux.dev,
	Niklas Schnelle <schnelle@...ux.ibm.com>,
	Will Deacon <will@...nel.org>
Subject: [PATCH 1/6] x86: Stop using weak symbols for __iowrite32_copy()

Start switching iomap_copy routines over to use #define and arch provided
inline/macro functions instead of weak symbols.

Inline functions allow more compiler optimization and this is often a
driver hot path.

x86 has the only weak implementation for __iowrite32_copy(), so replace it
with a static inline containing the same single instruction inline
assembly. The compiler will generate the "mov edx,ecx" in a more optimal
way.

Remove iomap_copy_64.S

Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
---
 arch/x86/include/asm/io.h    | 17 +++++++++++++++++
 arch/x86/lib/Makefile        |  1 -
 arch/x86/lib/iomap_copy_64.S | 15 ---------------
 include/linux/io.h           |  5 ++++-
 lib/iomap_copy.c             |  6 +++---
 5 files changed, 24 insertions(+), 20 deletions(-)
 delete mode 100644 arch/x86/lib/iomap_copy_64.S

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 3814a9263d64ea..2483988f0b7f7b 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -209,6 +209,23 @@ void memset_io(volatile void __iomem *, int, size_t);
 #define memcpy_toio memcpy_toio
 #define memset_io memset_io
 
+#ifdef CONFIG_X86_64
+/*
+ * Commit 0f07496144c2 ("[PATCH] Add faster __iowrite32_copy routine for
+ * x86_64") says that circa 2006 rep movsl is noticeably faster than a copy
+ * loop.
+ */
+static inline void __iowrite32_copy(void __iomem *to, const void *from,
+				    size_t count)
+{
+	asm volatile("rep ; movsl"
+		     : "=&c"(count), "=&D"(to), "=&S"(from)
+		     : "0"(count), "1"(to), "2"(from)
+		     : "memory");
+}
+#define __iowrite32_copy __iowrite32_copy
+#endif
+
 /*
  * ISA space is 'always mapped' on a typical x86 system, no need to
  * explicitly ioremap() it. The fact that the ISA IO space is mapped
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index ea3a28e7b613cc..af4ea3d83ba1f6 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -66,7 +66,6 @@ ifneq ($(CONFIG_X86_CMPXCHG64),y)
         lib-y += atomic64_386_32.o
 endif
 else
-        obj-y += iomap_copy_64.o
 ifneq ($(CONFIG_GENERIC_CSUM),y)
         lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
 endif
diff --git a/arch/x86/lib/iomap_copy_64.S b/arch/x86/lib/iomap_copy_64.S
deleted file mode 100644
index 6ff2f56cb0f71a..00000000000000
--- a/arch/x86/lib/iomap_copy_64.S
+++ /dev/null
@@ -1,15 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright 2006 PathScale, Inc.  All Rights Reserved.
- */
-
-#include <linux/linkage.h>
-
-/*
- * override generic version in lib/iomap_copy.c
- */
-SYM_FUNC_START(__iowrite32_copy)
-	movl %edx,%ecx
-	rep movsl
-	RET
-SYM_FUNC_END(__iowrite32_copy)
diff --git a/include/linux/io.h b/include/linux/io.h
index 7304f2a69960a3..68cd551b6af112 100644
--- a/include/linux/io.h
+++ b/include/linux/io.h
@@ -16,7 +16,10 @@
 struct device;
 struct resource;
 
-__visible void __iowrite32_copy(void __iomem *to, const void *from, size_t count);
+#ifndef __iowrite32_copy
+void __iowrite32_copy(void __iomem *to, const void *from, size_t count);
+#endif
+
 void __ioread32_copy(void *to, const void __iomem *from, size_t count);
 void __iowrite64_copy(void __iomem *to, const void *from, size_t count);
 
diff --git a/lib/iomap_copy.c b/lib/iomap_copy.c
index 5de7c04e05ef56..8ddcbb53507dfe 100644
--- a/lib/iomap_copy.c
+++ b/lib/iomap_copy.c
@@ -16,9 +16,8 @@
  * time.  Order of access is not guaranteed, nor is a memory barrier
  * performed afterwards.
  */
-void __attribute__((weak)) __iowrite32_copy(void __iomem *to,
-					    const void *from,
-					    size_t count)
+#ifndef __iowrite32_copy
+void __iowrite32_copy(void __iomem *to, const void *from, size_t count)
 {
 	u32 __iomem *dst = to;
 	const u32 *src = from;
@@ -28,6 +27,7 @@ void __attribute__((weak)) __iowrite32_copy(void __iomem *to,
 		__raw_writel(*src++, dst++);
 }
 EXPORT_SYMBOL_GPL(__iowrite32_copy);
+#endif
 
 /**
  * __ioread32_copy - copy data from MMIO space, in 32-bit units
-- 
2.43.2