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authorAnton Blanchard <anton@samba.org>2012-07-04 20:37:11 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2012-07-11 14:18:40 +1000
commit18ad51dd342a7eb09dbcd059d0b451b616d4dafc (patch)
tree94809605669eb3b5e4e049501958a2fa93ae2de7 /arch/powerpc/kernel/vdso32
parente6a74c6ea331b79c86e1898c504790b3dadc591d (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')
-rw-r--r--arch/powerpc/kernel/vdso32/Makefile4
-rw-r--r--arch/powerpc/kernel/vdso32/getcpu.S45
-rw-r--r--arch/powerpc/kernel/vdso32/vdso32.lds.S3
3 files changed, 51 insertions, 1 deletions
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 <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)
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: *;
};