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Subject[PATCH v4 1/8] powerpc/32: Add VDSO version of getcpu on non SMP
Date
Commit 18ad51dd342a ("powerpc: Add VDSO version of getcpu") added
getcpu() for PPC64 only, by making use of a user readable general
purpose SPR.

PPC32 doesn't have any such SPR.

For non SMP, just return CPU id 0 from the VDSO directly.
PPC32 doesn't support CONFIG_NUMA so NUMA node is always 0.

Before the patch, vdsotest reported:
getcpu: syscall: 1572 nsec/call
getcpu: libc: 1787 nsec/call
getcpu: vdso: not tested

Now, vdsotest reports:
getcpu: syscall: 1582 nsec/call
getcpu: libc: 502 nsec/call
getcpu: vdso: 187 nsec/call

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

---
v2: fixed build error in getcpu.S
v3: dropped the fast system call, only support non SMP for now.
---
arch/powerpc/kernel/vdso32/Makefile | 4 +---
arch/powerpc/kernel/vdso32/getcpu.S | 17 +++++++++++++++++
arch/powerpc/kernel/vdso32/vdso32.lds.S | 2 +-
3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 06f54d947057..e147bbdc12cd 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -2,9 +2,7 @@

# List of files in the vdso, has to be asm only for now

-obj-vdso32-$(CONFIG_PPC64) = getcpu.o
-obj-vdso32 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o \
- $(obj-vdso32-y)
+obj-vdso32 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o getcpu.o

# Build rules

diff --git a/arch/powerpc/kernel/vdso32/getcpu.S b/arch/powerpc/kernel/vdso32/getcpu.S
index 63e914539e1a..90b39af14383 100644
--- a/arch/powerpc/kernel/vdso32/getcpu.S
+++ b/arch/powerpc/kernel/vdso32/getcpu.S
@@ -15,6 +15,7 @@
* int __kernel_getcpu(unsigned *cpu, unsigned *node);
*
*/
+#if defined(CONFIG_PPC64)
V_FUNCTION_BEGIN(__kernel_getcpu)
.cfi_startproc
mfspr r5,SPRN_SPRG_VDSO_READ
@@ -31,3 +32,19 @@ V_FUNCTION_BEGIN(__kernel_getcpu)
blr
.cfi_endproc
V_FUNCTION_END(__kernel_getcpu)
+#elif !defined(CONFIG_SMP)
+V_FUNCTION_BEGIN(__kernel_getcpu)
+ .cfi_startproc
+ cmpwi cr0, r3, 0
+ cmpwi cr1, r4, 0
+ li r5, 0
+ beq cr0, 1f
+ stw r5, 0(r3)
+1: li r3, 0 /* always success */
+ crclr cr0*4+so
+ beqlr cr1
+ stw r5, 0(r4)
+ blr
+ .cfi_endproc
+V_FUNCTION_END(__kernel_getcpu)
+#endif
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 00c025ba4a92..5206c2eb2a1d 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -155,7 +155,7 @@ VERSION
__kernel_sync_dicache_p5;
__kernel_sigtramp32;
__kernel_sigtramp_rt32;
-#ifdef CONFIG_PPC64
+#if defined(CONFIG_PPC64) || !defined(CONFIG_SMP)
__kernel_getcpu;
#endif

--
2.13.3
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