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Subject[PATCH 3/5] -march=native: REP MOVSB support
Date
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@gmail.com>
---
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
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