diff options
| author | Anton Blanchard <anton@samba.org> | 2012-07-04 20:37:11 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2012-07-11 14:18:40 +1000 |
| commit | 18ad51dd342a7eb09dbcd059d0b451b616d4dafc (patch) | |
| tree | 94809605669eb3b5e4e049501958a2fa93ae2de7 /arch/powerpc/kernel/vdso32/getcpu.S | |
| parent | e6a74c6ea331b79c86e1898c504790b3dadc591d (diff) | |
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 <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/vdso32/getcpu.S')
| -rw-r--r-- | arch/powerpc/kernel/vdso32/getcpu.S | 45 |
1 files changed, 45 insertions, 0 deletions
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 <anton@au.ibm.com> + */ +#include <asm/ppc_asm.h> +#include <asm/vdso.h> + + .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) |