From 18ad51dd342a7eb09dbcd059d0b451b616d4dafc Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Wed, 4 Jul 2012 20:37:11 +0000 Subject: powerpc: Add VDSO version of getcpu We have a request for a fast method of getting CPU and NUMA node IDs from userspace. This patch implements a getcpu VDSO function, similar to x86. Ben suggested we use SPRG3 which is userspace readable. SPRG3 can be modified by a KVM guest, so we save the SPRG3 value in the paca and restore it when transitioning from the guest to the host. I have a glibc patch that implements sched_getcpu on top of this. Testing on a POWER7: baseline: 538 cycles vdso: 30 cycles Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/vdso32/Makefile | 4 ++- arch/powerpc/kernel/vdso32/getcpu.S | 45 +++++++++++++++++++++++++++++++++ arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 +++ 3 files changed, 51 insertions(+), 1 deletion(-) create mode 100644 arch/powerpc/kernel/vdso32/getcpu.S (limited to 'arch/powerpc/kernel/vdso32') diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile index 9a7946c41738..53e6c9b979ec 100644 --- a/arch/powerpc/kernel/vdso32/Makefile +++ b/arch/powerpc/kernel/vdso32/Makefile @@ -1,7 +1,9 @@ # List of files in the vdso, has to be asm only for now -obj-vdso32 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o +obj-vdso32-$(CONFIG_PPC64) = getcpu.o +obj-vdso32 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o \ + $(obj-vdso32-y) # Build rules diff --git a/arch/powerpc/kernel/vdso32/getcpu.S b/arch/powerpc/kernel/vdso32/getcpu.S new file mode 100644 index 000000000000..47afd08c90f7 --- /dev/null +++ b/arch/powerpc/kernel/vdso32/getcpu.S @@ -0,0 +1,45 @@ +/* + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright (C) IBM Corporation, 2012 + * + * Author: Anton Blanchard + */ +#include +#include + + .text +/* + * Exact prototype of getcpu + * + * int __kernel_getcpu(unsigned *cpu, unsigned *node); + * + */ +V_FUNCTION_BEGIN(__kernel_getcpu) + .cfi_startproc + mfspr r5,SPRN_USPRG3 + cmpdi cr0,r3,0 + cmpdi cr1,r4,0 + clrlwi r6,r5,16 + rlwinm r7,r5,16,31-15,31-0 + beq cr0,1f + stw r6,0(r3) +1: beq cr1,2f + stw r7,0(r4) +2: crclr cr0*4+so + li r3,0 /* always success */ + blr + .cfi_endproc +V_FUNCTION_END(__kernel_getcpu) diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S index 0546bcd49cd0..43200ba2e570 100644 --- a/arch/powerpc/kernel/vdso32/vdso32.lds.S +++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S @@ -147,6 +147,9 @@ VERSION __kernel_sync_dicache_p5; __kernel_sigtramp32; __kernel_sigtramp_rt32; +#ifdef CONFIG_PPC64 + __kernel_getcpu; +#endif local: *; }; -- cgit v1.2.3