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Subject[PATCH 3/5] x86_64, -march=native: REP MOVSB support
Date
Detect fast REP MOVSB support and use it for page copying.

Inline copy_page(), this saves alternative entry and a function call
overhead which should hopefully improve code generation.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
Makefile | 3 +++
arch/x86/include/asm/page_64.h | 13 +++++++++++++
arch/x86/kernel/relocate_kernel_64.S | 15 +++++++++++++++
arch/x86/kernel/verify_cpu.S | 12 ++++++++++++
arch/x86/lib/Makefile | 5 ++++-
arch/x86/lib/memcpy_64.S | 13 +++++++++++++
arch/x86/platform/pvh/head.S | 4 ++++
scripts/kconfig/cpuid.c | 9 +++++++++
scripts/march-native.sh | 1 +
9 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 690f70afa74e..aa194c96d27c 100644
--- a/Makefile
+++ b/Makefile
@@ -609,6 +609,9 @@ endif
ifdef CONFIG_MARCH_NATIVE
KBUILD_CFLAGS += -march=native
endif
+ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+KBUILD_CFLAGS += -mmemcpy-strategy=rep_byte:-1:align,rep_byte:-1:noalign
+endif

ifeq ($(KBUILD_EXTMOD),)
# Objects we will link into vmlinux / subdirs we need to visit
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index 939b1cff4a7b..051da768273d 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -54,7 +54,20 @@ static inline void clear_page(void *page)
: "cc", "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

#endif /* !__ASSEMBLY__ */

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index c51ccff5cd01..822f7a3d035a 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -266,18 +266,33 @@ 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/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S
index a9be8904faa3..57b41dafc592 100644
--- a/arch/x86/kernel/verify_cpu.S
+++ b/arch/x86/kernel/verify_cpu.S
@@ -142,6 +142,18 @@ ENTRY(verify_cpu)
jnc .Lverify_cpu_no_longmode
#endif

+#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
+ xor %eax, %eax
+ cpuid
+ cmp $7, %eax
+ jb .Lverify_cpu_no_longmode
+ mov $7, %eax
+ xor %ecx, %ecx
+ cpuid
+ bt $9, %ebx
+ jnc .Lverify_cpu_no_longmode
+#endif
+
popf # Restore caller passed flags
xorl %eax, %eax
ret
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 7dc0e71b0ef3..fa24cc717fb1 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -59,7 +59,10 @@ endif
else
obj-y += iomap_copy_64.o
lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
- lib-y += clear_page_64.o copy_page_64.o
+ lib-y += clear_page_64.o
+ifneq ($(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 92748660ba51..ab5b9662b348 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -17,6 +17,18 @@

.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.
*
@@ -183,6 +195,7 @@ ENTRY(memcpy_orig)
.Lend:
retq
ENDPROC(memcpy_orig)
+#endif

#ifndef CONFIG_UML

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 1f8825bbaffb..2737f3e8c021 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -64,9 +64,13 @@ 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 9efc0d9464d8..2d78fba1dcc7 100644
--- a/scripts/kconfig/cpuid.c
+++ b/scripts/kconfig/cpuid.c
@@ -44,6 +44,7 @@ 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;

@@ -59,6 +60,13 @@ static void intel(void)
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[])
@@ -79,6 +87,7 @@ 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 c3059f93ed2b..87f00cdb8e10 100755
--- a/scripts/march-native.sh
+++ b/scripts/march-native.sh
@@ -42,6 +42,7 @@ COLLECT_GCC_OPTIONS=$(
echo "-march=native: $COLLECT_GCC_OPTIONS"

"$CPUID" popcnt && option "CONFIG_MARCH_NATIVE_POPCNT"
+"$CPUID" rep_movsb && option "CONFIG_MARCH_NATIVE_REP_MOVSB"

for i in $COLLECT_GCC_OPTIONS; do
case $i in
--
2.21.0
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