[PATCH 3/5] -march=native: REP MOVSB support

[Alexey Dobriyan]

If CPU advertises fast REP MOVSB, use it.

Inline copy_page() to use only 3 registers across function call
not whole shebang as required by ABI.

Also, tell gcc to use REP MOVSB for memcpy(), this saves terabytes of .text.

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---
 Makefile                             |  3 +++
 arch/x86/include/asm/page_64.h       | 13 +++++++++++++
 arch/x86/kernel/relocate_kernel_64.S | 15 +++++++++++++++
 arch/x86/lib/Makefile                |  5 ++++-
 arch/x86/lib/memcpy_64.S             | 13 +++++++++++++
 arch/x86/xen/xen-pvh.S               |  4 ++++
 scripts/kconfig/cpuid.c              |  9 +++++++++
 scripts/march-native.sh              |  1 +
 8 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index c1cc730b81a8..84abac4c181a 100644
--- a/Makefile
+++ b/Makefile
@@ -590,6 +590,9 @@ ifeq ($(dot-config),1)
 ifdef CONFIG_MARCH_NATIVE
 KBUILD_CFLAGS += -march=native
 endif
+ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+KBUILD_CFLAGS += -mmemcpy-strategy=rep_byte:-1:align
+endif
 
 ifeq ($(KBUILD_EXTMOD),)
 # Read in dependencies to all Kconfig* files, make sure to run
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index 4baa6bceb232..c2353661eaf1 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -50,7 +50,20 @@ static inline void clear_page(void *page)
 			   : "memory", "rax", "rcx");
 }
 
+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+static __always_inline void copy_page(void *to, void *from)
+{
+	uint32_t len = PAGE_SIZE;
+	asm volatile (
+		"rep movsb"
+		: "+D" (to), "+S" (from), "+c" (len)
+		:
+		: "memory"
+	);
+}
+#else
 void copy_page(void *to, void *from);
+#endif
 
 #ifdef CONFIG_X86_MCE
 #define arch_unmap_kpfn arch_unmap_kpfn
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 307d3bac5f04..6ccfb9a63d5c 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -260,18 +260,33 @@ swap_pages:
 	movq	%rsi, %rax
 
 	movq	%r10, %rdi
+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+	mov	$4096, %ecx
+	rep movsb
+#else
 	movl	$512, %ecx
 	rep ; movsq
+#endif
 
 	movq	%rax, %rdi
 	movq	%rdx, %rsi
+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+	mov	$4096, %ecx
+	rep movsb
+#else
 	movl	$512, %ecx
 	rep ; movsq
+#endif
 
 	movq	%rdx, %rdi
 	movq	%r10, %rsi
+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+	mov	$4096, %ecx
+	rep movsb
+#else
 	movl	$512, %ecx
 	rep ; movsq
+#endif
 
 	lea	PAGE_SIZE(%rax), %rsi
 	jmp	0b
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index c26ad76e7048..8f9460bef2ec 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -45,7 +45,10 @@ endif
 else
         obj-y += iomap_copy_64.o
         lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
-        lib-y += clear_page_64.o copy_page_64.o
+        lib-y += clear_page_64.o
+ifneq ($(CONFIG_MARCH_NATIVE_REP_MOVSB),y)
+	lib-y += copy_page_64.o
+endif
         lib-y += memmove_64.o memset_64.o
         lib-y += copy_user_64.o
 	lib-y += cmpxchg16b_emu.o
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 9a53a06e5a3e..28a807eb9bd6 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -15,6 +15,18 @@
 
 .weak memcpy
 
+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+ENTRY(__memcpy)
+ENTRY(memcpy)
+	mov	%rdi, %rax
+	mov	%rdx, %rcx
+	rep movsb
+	ret
+ENDPROC(memcpy)
+ENDPROC(__memcpy)
+EXPORT_SYMBOL(memcpy)
+EXPORT_SYMBOL(__memcpy)
+#else
 /*
  * memcpy - Copy a memory block.
  *
@@ -181,6 +193,7 @@ ENTRY(memcpy_orig)
 .Lend:
 	retq
 ENDPROC(memcpy_orig)
+#endif
 
 #ifndef CONFIG_UML
 /*
diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S
index e1a5fbeae08d..1dc30f0dfdf7 100644
--- a/arch/x86/xen/xen-pvh.S
+++ b/arch/x86/xen/xen-pvh.S
@@ -68,9 +68,13 @@ ENTRY(pvh_start_xen)
 	mov $_pa(pvh_start_info), %edi
 	mov %ebx, %esi
 	mov _pa(pvh_start_info_sz), %ecx
+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+	rep movsb
+#else
 	shr $2,%ecx
 	rep
 	movsl
+#endif
 
 	mov $_pa(early_stack_end), %esp
 
diff --git a/scripts/kconfig/cpuid.c b/scripts/kconfig/cpuid.c
index e565dd446bdf..4947f47e7728 100644
--- a/scripts/kconfig/cpuid.c
+++ b/scripts/kconfig/cpuid.c
@@ -43,6 +43,7 @@ static inline void cpuid2(uint32_t eax0, uint32_t ecx0, uint32_t *eax, uint32_t
 }
 
 static bool popcnt	= false;
+static bool rep_movsb	= false;
 
 static uint32_t eax0_max;
 
@@ -57,6 +58,13 @@ static void intel(void)
 		if (ecx & (1 << 23))
 			popcnt = true;
 	}
+	if (eax0_max >= 7) {
+		cpuid2(7, 0, &eax, &ecx, &edx, &ebx);
+//		printf("%08x %08x %08x %08x\n", eax, ecx, edx, ebx);
+
+		if (ebx & (1 << 9))
+			rep_movsb = true;
+	}
 }
 
 int main(int argc, char *argv[])
@@ -76,6 +84,7 @@ int main(int argc, char *argv[])
 
 #define _(x)	if (streq(opt, #x)) return x ? EXIT_SUCCESS : EXIT_FAILURE
 	_(popcnt);
+	_(rep_movsb);
 #undef _
 
 	return EXIT_FAILURE;
diff --git a/scripts/march-native.sh b/scripts/march-native.sh
index 6641e356b646..eb52c20c56b4 100755
--- a/scripts/march-native.sh
+++ b/scripts/march-native.sh
@@ -31,6 +31,7 @@ option() {
 
 if test -x "$CPUID"; then
 	"$CPUID" popcnt		&& option "CONFIG_MARCH_NATIVE_POPCNT"
+	"$CPUID" rep_movsb	&& option "CONFIG_MARCH_NATIVE_REP_MOVSB"
 fi
 
 if test ! -f "$AUTOCONF1" -o ! -f "$AUTOCONF2"; then
-- 
2.13.6