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/reg.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'arch/powerpc/include/asm/reg.h') diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index f0cb7f461b9d..2baeb7c8764f 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -491,6 +491,7 @@ #define SPRN_SPRG1 0x111 /* Special Purpose Register General 1 */ #define SPRN_SPRG2 0x112 /* Special Purpose Register General 2 */ #define SPRN_SPRG3 0x113 /* Special Purpose Register General 3 */ +#define SPRN_USPRG3 0x103 /* SPRG3 userspace read */ #define SPRN_SPRG4 0x114 /* Special Purpose Register General 4 */ #define SPRN_SPRG5 0x115 /* Special Purpose Register General 5 */ #define SPRN_SPRG6 0x116 /* Special Purpose Register General 6 */ @@ -753,14 +754,14 @@ * 64-bit server: * - SPRG0 unused (reserved for HV on Power4) * - SPRG2 scratch for exception vectors - * - SPRG3 unused (user visible) + * - SPRG3 CPU and NUMA node for VDSO getcpu (user visible) * - HSPRG0 stores PACA in HV mode * - HSPRG1 scratch for "HV" exceptions * * 64-bit embedded * - SPRG0 generic exception scratch * - SPRG2 TLB exception stack - * - SPRG3 unused (user visible) + * - SPRG3 CPU and NUMA node for VDSO getcpu (user visible) * - SPRG4 unused (user visible) * - SPRG6 TLB miss scratch (user visible, sorry !) * - SPRG7 critical exception scratch -- cgit v1.2.3 From b416c9a10baae6a177b4f9ee858b8d309542fbef Mon Sep 17 00:00:00 2001 From: Tiejun Chen Date: Wed, 11 Jul 2012 14:22:46 +1000 Subject: powerpc: Add "memory" attribute for mfmsr() Add "memory" attribute in inline assembly language as a compiler barrier to make sure 4.6.x GCC don't reorder mfmsr(). Signed-off-by: Tiejun Chen Signed-off-by: Benjamin Herrenschmidt CC: stable@vger.kernel.org --- arch/powerpc/include/asm/reg.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/include/asm/reg.h') diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index 2baeb7c8764f..638608677e2a 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -1025,7 +1025,8 @@ /* Macros for setting and retrieving special purpose registers */ #ifndef __ASSEMBLY__ #define mfmsr() ({unsigned long rval; \ - asm volatile("mfmsr %0" : "=r" (rval)); rval;}) + asm volatile("mfmsr %0" : "=r" (rval) : \ + : "memory"); rval;}) #ifdef CONFIG_PPC_BOOK3S_64 #define __mtmsrd(v, l) asm volatile("mtmsrd %0," __stringify(l) \ : : "r" (v) : "memory") -- cgit v1.2.3