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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/include/asm/kvm_book3s_asm.h
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/include/asm/kvm_book3s_asm.h')
-rw-r--r--arch/powerpc/include/asm/kvm_book3s_asm.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
index 88609b23b775..bfcd00c1485d 100644
--- a/arch/powerpc/include/asm/kvm_book3s_asm.h
+++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
@@ -74,6 +74,7 @@ struct kvmppc_host_state {
ulong vmhandler;
ulong scratch0;
ulong scratch1;
+ ulong sprg3;
u8 in_guest;
u8 restore_hid5;
u8 napping;

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