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Message-Id: <a5e7187e0464f48cac6980b4c20e902039b19cc1.1578934751.git.christophe.leroy@c-s.fr>
In-Reply-To: <cover.1578934751.git.christophe.leroy@c-s.fr>
References: <cover.1578934751.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [RFC PATCH v3 10/12] powerpc/vdso: provide vdso data pointer from the
 ASM caller.
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, arnd@arndb.de,
        tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
        x86@kernel.org
Date:   Mon, 13 Jan 2020 17:08:48 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

__arch_get_vdso_data() clobbers the link register, requiring
the caller to save it.

As the ASM calling function already has to set a stack frame and
saves the link register before calling the C vdso function,
retriving the vdso data pointer there is lighter.

The improvement is significant:

Before:
gettimeofday:    vdso: 1027 nsec/call
clock-getres-realtime-coarse:    vdso: 699 nsec/call
clock-gettime-realtime-coarse:    vdso: 784 nsec/call
clock-gettime-realtime:    vdso: 1231 nsec/call

After:
gettimeofday:    vdso: 908 nsec/call
clock-getres-realtime-coarse:    vdso: 545 nsec/call
clock-gettime-realtime-coarse:    vdso: 617 nsec/call
clock-gettime-realtime:    vdso: 1078 nsec/call

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/include/asm/vdso/gettimeofday.h | 12 ++----------
 arch/powerpc/kernel/vdso32/gettimeofday.S    |  3 +++
 arch/powerpc/kernel/vdso32/vgettimeofday.c   | 19 +++++++++++--------
 arch/powerpc/kernel/vdso64/gettimeofday.S    |  3 +++
 arch/powerpc/kernel/vdso64/vgettimeofday.c   | 19 +++++++++++--------
 5 files changed, 30 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h b/arch/powerpc/include/asm/vdso/gettimeofday.h
index 343c81a7e951..d1e702e0ea86 100644
--- a/arch/powerpc/include/asm/vdso/gettimeofday.h
+++ b/arch/powerpc/include/asm/vdso/gettimeofday.h
@@ -6,13 +6,14 @@
 
 #include <asm/time.h>
 #include <asm/unistd.h>
-#include <asm/vdso_datapage.h>
 #include <uapi/linux/time.h>
 
 #define VDSO_HAS_CLOCK_GETRES		1
 
 #define VDSO_HAS_TIME			1
 
+#define VDSO_GETS_VD_PTR_FROM_ARCH	1
+
 static __always_inline int do_syscall_2(const unsigned long _r0, const unsigned long _r3,
 					const unsigned long _r4)
 {
@@ -80,15 +81,6 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
 	return get_tb();
 }
 
-void *__get_datapage(void);
-
-static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
-{
-	struct vdso_arch_data *vdso_data = __get_datapage();
-
-	return vdso_data->data;
-}
-
 /*
  * powerpc specific delta calculation.
  *
diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index ba0bd64b3da3..0d43878e462c 100644
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
@@ -9,6 +9,7 @@
 #include <asm/processor.h>
 #include <asm/ppc_asm.h>
 #include <asm/vdso.h>
+#include <asm/vdso_datapage.h>
 #include <asm/asm-offsets.h>
 #include <asm/unistd.h>
 
@@ -18,6 +19,7 @@
 	stwu	r1, -16(r1)
 	mflr	r0
 	stw	r0, 20(r1)
+	get_datapage	r5, VDSO_DATA_OFFSET
 	bl	\funct
 	lwz	r0, 20(r1)
 	cmpwi	r3, 0
@@ -79,6 +81,7 @@ V_FUNCTION_BEGIN(__kernel_time)
 	stwu	r1, -16(r1)
 	mflr	r0
 	stw	r0, 20(r1)
+	get_datapage	r4, VDSO_DATA_OFFSET
 	bl	__c_kernel_time
 	lwz	r0, 20(r1)
 	crclr	cr0*4+so
diff --git a/arch/powerpc/kernel/vdso32/vgettimeofday.c b/arch/powerpc/kernel/vdso32/vgettimeofday.c
index 4ed1bf2ae30e..7fdccf896a9c 100644
--- a/arch/powerpc/kernel/vdso32/vgettimeofday.c
+++ b/arch/powerpc/kernel/vdso32/vgettimeofday.c
@@ -5,22 +5,25 @@
 #include <linux/time.h>
 #include <linux/types.h>
 
-int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts)
+int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,
+			     const struct vdso_data *vd)
 {
-	return __cvdso_clock_gettime32(clock, ts);
+	return __cvdso_clock_gettime32(vd, clock, ts);
 }
 
-int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
+int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,
+			    const struct vdso_data *vd)
 {
-	return __cvdso_gettimeofday(tv, tz);
+	return __cvdso_gettimeofday(vd, tv, tz);
 }
 
-int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res)
+int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res,
+			    const struct vdso_data *vd)
 {
-	return __cvdso_clock_getres_time32(clock_id, res);
+	return __cvdso_clock_getres_time32(vd, clock_id, res);
 }
 
-time_t __c_kernel_time(time_t *time)
+time_t __c_kernel_time(time_t *time, const struct vdso_data *vd)
 {
-	return __cvdso_time(time);
+	return __cvdso_time(vd, time);
 }
diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S b/arch/powerpc/kernel/vdso64/gettimeofday.S
index 22f4f1f73bbc..f61c53eb6600 100644
--- a/arch/powerpc/kernel/vdso64/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso64/gettimeofday.S
@@ -9,6 +9,7 @@
 #include <asm/processor.h>
 #include <asm/ppc_asm.h>
 #include <asm/vdso.h>
+#include <asm/vdso_datapage.h>
 #include <asm/asm-offsets.h>
 #include <asm/unistd.h>
 
@@ -18,6 +19,7 @@
 	mflr	r0
 	std	r0, 16(r1)
 	stdu	r1, -128(r1)
+	get_datapage	r5, VDSO_DATA_OFFSET
 	bl	\funct
 	addi	r1, r1, 128
 	ld	r0, 16(r1)
@@ -79,6 +81,7 @@ V_FUNCTION_BEGIN(__kernel_time)
 	mflr	r0
 	std	r0, 16(r1)
 	stdu	r1, -128(r1)
+	get_datapage	r4, VDSO_DATA_OFFSET
 	bl	__c_kernel_time
 	addi	r1, r1, 128
 	ld	r0, 16(r1)
diff --git a/arch/powerpc/kernel/vdso64/vgettimeofday.c b/arch/powerpc/kernel/vdso64/vgettimeofday.c
index 407c6a7ed4e2..4917d7a92a0c 100644
--- a/arch/powerpc/kernel/vdso64/vgettimeofday.c
+++ b/arch/powerpc/kernel/vdso64/vgettimeofday.c
@@ -5,22 +5,25 @@
 #include <linux/time.h>
 #include <linux/types.h>
 
-int __c_kernel_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
+int __c_kernel_clock_gettime(clockid_t clock, struct __kernel_timespec *ts,
+			     const struct vdso_data *vd)
 {
-	return __cvdso_clock_gettime(clock, ts);
+	return __cvdso_clock_gettime(vd, clock, ts);
 }
 
-int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
+int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,
+			    const struct vdso_data *vd)
 {
-	return __cvdso_gettimeofday(tv, tz);
+	return __cvdso_gettimeofday(vd, tv, tz);
 }
 
-int __c_kernel_clock_getres(clockid_t clock_id, struct __kernel_timespec *res)
+int __c_kernel_clock_getres(clockid_t clock_id, struct __kernel_timespec *res,
+			    const struct vdso_data *vd)
 {
-	return __cvdso_clock_getres(clock_id, res);
+	return __cvdso_clock_getres(vd, clock_id, res);
 }
 
-time_t __c_kernel_time(time_t *time)
+time_t __c_kernel_time(time_t *time, const struct vdso_data *vd)
 {
-	return __cvdso_time(time);
+	return __cvdso_time(vd, time);
 }
-- 
2.13.3