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powerpc/32: Add VDSO version of getcpu on non SMP 

Commit 18ad51dd34 ("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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/eaac4b6494ecff1811220fccc895bf282aab884a.1575273217.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy 2019-12-02 07:57:27 +00:00 committed by Michael Ellerman
parent 8c452a8898
commit 902137ba8e
3 changed files with 19 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/kernel/vdso32/Makefile
View File

@ -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

17
arch/powerpc/kernel/vdso32/getcpu.S
View File

@ -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

2
arch/powerpc/kernel/vdso32/vdso32.lds.S
View File

@ -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