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/include/asm/kvm_book3s_asm.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/powerpc/include/asm/kvm_book3s_asm.h') 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; -- cgit