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Message-Id: <65f1ed51b9cff219b9380c81d88353570cafdfd3.1565966871.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH] powerpc/vdso32: inline __get_datapage()
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Date:   Fri, 16 Aug 2019 14:48:48 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

__get_datapage() is only a few instructions to retrieve the
address of the page where the kernel stores data to the VDSO.

By inlining this function into its users, a bl/blr pair and
a mflr/mtlr pair is avoided, plus a few reg moves.

The improvement is noticeable (about 55 nsec/call on an 8xx)

vdsotest before the patch:
gettimeofday:    vdso: 731 nsec/call
clock-gettime-realtime-coarse:    vdso: 668 nsec/call
clock-gettime-monotonic-coarse:    vdso: 745 nsec/call

vdsotest after the patch:
gettimeofday:    vdso: 677 nsec/call
clock-gettime-realtime-coarse:    vdso: 613 nsec/call
clock-gettime-monotonic-coarse:    vdso: 690 nsec/call

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/vdso32/cacheflush.S   | 10 +++++-----
 arch/powerpc/kernel/vdso32/datapage.S     | 29 ++++-------------------------
 arch/powerpc/kernel/vdso32/datapage.h     | 12 ++++++++++++
 arch/powerpc/kernel/vdso32/gettimeofday.S | 11 +++++------
 4 files changed, 26 insertions(+), 36 deletions(-)
 create mode 100644 arch/powerpc/kernel/vdso32/datapage.h

diff --git a/arch/powerpc/kernel/vdso32/cacheflush.S b/arch/powerpc/kernel/vdso32/cacheflush.S
index 7f882e7b9f43..e9453837e4ee 100644
--- a/arch/powerpc/kernel/vdso32/cacheflush.S
+++ b/arch/powerpc/kernel/vdso32/cacheflush.S
@@ -10,6 +10,8 @@
 #include <asm/vdso.h>
 #include <asm/asm-offsets.h>
 
+#include "datapage.h"
+
 	.text
 
 /*
@@ -24,14 +26,12 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache)
   .cfi_startproc
 	mflr	r12
   .cfi_register lr,r12
-	mr	r11,r3
-	bl	__get_datapage@local
+	get_datapage	r10, r0
 	mtlr	r12
-	mr	r10,r3
 
 	lwz	r7,CFG_DCACHE_BLOCKSZ(r10)
 	addi	r5,r7,-1
-	andc	r6,r11,r5		/* round low to line bdy */
+	andc	r6,r3,r5		/* round low to line bdy */
 	subf	r8,r6,r4		/* compute length */
 	add	r8,r8,r5		/* ensure we get enough */
 	lwz	r9,CFG_DCACHE_LOGBLOCKSZ(r10)
@@ -48,7 +48,7 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache)
 
 	lwz	r7,CFG_ICACHE_BLOCKSZ(r10)
 	addi	r5,r7,-1
-	andc	r6,r11,r5		/* round low to line bdy */
+	andc	r6,r3,r5		/* round low to line bdy */
 	subf	r8,r6,r4		/* compute length */
 	add	r8,r8,r5
 	lwz	r9,CFG_ICACHE_LOGBLOCKSZ(r10)
diff --git a/arch/powerpc/kernel/vdso32/datapage.S b/arch/powerpc/kernel/vdso32/datapage.S
index 6984125b9fc0..d480d2d4a3fe 100644
--- a/arch/powerpc/kernel/vdso32/datapage.S
+++ b/arch/powerpc/kernel/vdso32/datapage.S
@@ -11,34 +11,13 @@
 #include <asm/unistd.h>
 #include <asm/vdso.h>
 
+#include "datapage.h"
+
 	.text
 	.global	__kernel_datapage_offset;
 __kernel_datapage_offset:
 	.long	0
 
-V_FUNCTION_BEGIN(__get_datapage)
-  .cfi_startproc
-	/* We don't want that exposed or overridable as we want other objects
-	 * to be able to bl directly to here
-	 */
-	.protected __get_datapage
-	.hidden __get_datapage
-
-	mflr	r0
-  .cfi_register lr,r0
-
-	bcl	20,31,data_page_branch
-data_page_branch:
-	mflr	r3
-	mtlr	r0
-	addi	r3, r3, __kernel_datapage_offset-data_page_branch
-	lwz	r0,0(r3)
-  .cfi_restore lr
-	add	r3,r0,r3
-	blr
-  .cfi_endproc
-V_FUNCTION_END(__get_datapage)
-
 /*
  * void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
  *
@@ -53,7 +32,7 @@ V_FUNCTION_BEGIN(__kernel_get_syscall_map)
 	mflr	r12
   .cfi_register lr,r12
 	mr	r4,r3
-	bl	__get_datapage@local
+	get_datapage	r3, r0
 	mtlr	r12
 	addi	r3,r3,CFG_SYSCALL_MAP32
 	cmpli	cr0,r4,0
@@ -74,7 +53,7 @@ V_FUNCTION_BEGIN(__kernel_get_tbfreq)
   .cfi_startproc
 	mflr	r12
   .cfi_register lr,r12
-	bl	__get_datapage@local
+	get_datapage	r3, r0
 	lwz	r4,(CFG_TB_TICKS_PER_SEC + 4)(r3)
 	lwz	r3,CFG_TB_TICKS_PER_SEC(r3)
 	mtlr	r12
diff --git a/arch/powerpc/kernel/vdso32/datapage.h b/arch/powerpc/kernel/vdso32/datapage.h
new file mode 100644
index 000000000000..ad96256be090
--- /dev/null
+++ b/arch/powerpc/kernel/vdso32/datapage.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+.macro get_datapage ptr, tmp
+	bcl	20,31,888f
+888:
+	mflr	\ptr
+	addi	\ptr, \ptr, __kernel_datapage_offset - 888b
+	lwz	\tmp, 0(\ptr)
+	add	\ptr, \tmp, \ptr
+.endm
+
+
diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index e10098cde89c..91a58f01dcd5 100644
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
@@ -12,6 +12,8 @@
 #include <asm/asm-offsets.h>
 #include <asm/unistd.h>
 
+#include "datapage.h"
+
 /* Offset for the low 32-bit part of a field of long type */
 #ifdef CONFIG_PPC64
 #define LOPART	4
@@ -35,8 +37,7 @@ V_FUNCTION_BEGIN(__kernel_gettimeofday)
 
 	mr	r10,r3			/* r10 saves tv */
 	mr	r11,r4			/* r11 saves tz */
-	bl	__get_datapage@local	/* get data page */
-	mr	r9, r3			/* datapage ptr in r9 */
+	get_datapage	r9, r0
 	cmplwi	r10,0			/* check if tv is NULL */
 	beq	3f
 	lis	r7,1000000@ha		/* load up USEC_PER_SEC */
@@ -82,8 +83,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
 	mflr	r12			/* r12 saves lr */
   .cfi_register lr,r12
 	mr	r11,r4			/* r11 saves tp */
-	bl	__get_datapage@local	/* get data page */
-	mr	r9,r3			/* datapage ptr in r9 */
+	get_datapage	r9, r0
 	lis	r7,NSEC_PER_SEC@h	/* want nanoseconds */
 	ori	r7,r7,NSEC_PER_SEC@l
 	beq	cr5,70f
@@ -235,8 +235,7 @@ V_FUNCTION_BEGIN(__kernel_time)
   .cfi_register lr,r12
 
 	mr	r11,r3			/* r11 holds t */
-	bl	__get_datapage@local
-	mr	r9, r3			/* datapage ptr in r9 */
+	get_datapage	r9, r0
 
 	lwz	r3,STAMP_XTIME+TSPEC_TV_SEC(r9)
 
-- 
2.13.3