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Message-Id: <740c6923c313ff0c0c2394480d5691465919b52f.1565953624.git.christophe.leroy@c-s.fr>
Date: Fri, 16 Aug 2019 11:08:28 +0000 (UTC)
From: Christophe Leroy <christophe.leroy@....fr>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/32: Add VDSO version of getcpu
Commit 18ad51dd342a ("powerpc: Add VDSO version of getcpu") added
getcpu() for PPC64 only, by making use of a user readable general
purpose SPR.
PPC32 doesn't have any such SPR, a full system call can still be
avoided by implementing a fast system call which reads the CPU id
in the task struct and returns immediately without going back in
virtual mode.
Before the patch, vdsotest reported:
getcpu: syscall: 1572 nsec/call
getcpu: libc: 1787 nsec/call
getcpu: vdso: not tested
Now, vdsotest reports:
getcpu: syscall: 1582 nsec/call
getcpu: libc: 667 nsec/call
getcpu: vdso: 368 nsec/call
For non SMP, just return CPU id 0 from the VDSO directly.
PPC32 doesn't support CONFIG_NUMA so NUMA node is always 0.
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
arch/powerpc/include/asm/vdso.h | 2 ++
arch/powerpc/kernel/head_32.h | 13 +++++++++++++
arch/powerpc/kernel/head_booke.h | 11 +++++++++++
arch/powerpc/kernel/vdso32/Makefile | 4 +---
arch/powerpc/kernel/vdso32/getcpu.S | 7 +++++++
arch/powerpc/kernel/vdso32/vdso32.lds.S | 2 --
6 files changed, 34 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
index b5e1f8f8a05c..adb54782df5f 100644
--- a/arch/powerpc/include/asm/vdso.h
+++ b/arch/powerpc/include/asm/vdso.h
@@ -16,6 +16,8 @@
/* Define if 64 bits VDSO has procedure descriptors */
#undef VDS64_HAS_DESCRIPTORS
+#define NR_MAGIC_FAST_VDSO_SYSCALL 0x789a
+
#ifndef __ASSEMBLY__
/* Offsets relative to thread->vdso_base */
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 4a692553651f..a2e38b59785a 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -3,6 +3,8 @@
#define __HEAD_32_H__
#include <asm/ptrace.h> /* for STACK_FRAME_REGS_MARKER */
+#include <asm/vdso.h>
+#include <asm/asm-offsets.h>
/*
* MSR_KERNEL is > 0x8000 on 4xx/Book-E since it include MSR_CE.
@@ -74,7 +76,13 @@
.endm
.macro SYSCALL_ENTRY trapno
+#ifdef CONFIG_SMP
+ cmplwi cr0, r0, NR_MAGIC_FAST_VDSO_SYSCALL
+#endif
mfspr r12,SPRN_SPRG_THREAD
+#ifdef CONFIG_SMP
+ beq- 1f
+#endif
mfcr r10
lwz r11,TASK_STACK-THREAD(r12)
mflr r9
@@ -152,6 +160,11 @@
mtspr SPRN_SRR0,r11
SYNC
RFI /* jump to handler, enable MMU */
+#ifdef CONFIG_SMP
+1:
+ lwz r5, TASK_CPU - THREAD(r12)
+ RFI
+#endif
.endm
/*
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 2ae635df9026..c534e87cac84 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -3,6 +3,8 @@
#define __HEAD_BOOKE_H__
#include <asm/ptrace.h> /* for STACK_FRAME_REGS_MARKER */
+#include <asm/vdso.h>
+#include <asm/asm-offsets.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_booke_hv_asm.h>
@@ -104,6 +106,10 @@ FTR_SECTION_ELSE
#ifdef CONFIG_KVM_BOOKE_HV
ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
#endif
+#ifdef CONFIG_SMP
+ cmplwi cr0, r0, NR_MAGIC_FAST_VDSO_SYSCALL
+ beq- 1f
+#endif
BOOKE_CLEAR_BTB(r11)
lwz r11, TASK_STACK - THREAD(r10)
rlwinm r12,r12,0,4,2 /* Clear SO bit in CR */
@@ -176,6 +182,11 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
mtspr SPRN_SRR0,r11
SYNC
RFI /* jump to handler, enable MMU */
+#ifdef CONFIG_SMP
+1:
+ lwz r5, TASK_CPU - THREAD(r10)
+ RFI
+#endif
.endm
/* To handle the additional exception priority levels on 40x and Book-E
diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 06f54d947057..e147bbdc12cd 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -2,9 +2,7 @@
# List of files in the vdso, has to be asm only for now
-obj-vdso32-$(CONFIG_PPC64) = getcpu.o
-obj-vdso32 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o \
- $(obj-vdso32-y)
+obj-vdso32 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o getcpu.o
# Build rules
diff --git a/arch/powerpc/kernel/vdso32/getcpu.S b/arch/powerpc/kernel/vdso32/getcpu.S
index 63e914539e1a..bd67a0c25c86 100644
--- a/arch/powerpc/kernel/vdso32/getcpu.S
+++ b/arch/powerpc/kernel/vdso32/getcpu.S
@@ -17,7 +17,14 @@
*/
V_FUNCTION_BEGIN(__kernel_getcpu)
.cfi_startproc
+#if defined(CONFIG_PPC64)
mfspr r5,SPRN_SPRG_VDSO_READ
+#elif defined (CONFIG_SMP)*/
+ li r0, NR_MAGIC_FAST_VDSO_SYSCALL
+ sc /* returns cpuid in r5, clobbers cr0 and r10-r13 */
+#else
+ li r5, 0
+#endif
cmpwi cr0,r3,0
cmpwi cr1,r4,0
clrlwi r6,r5,16
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 099a6db14e67..663880671e20 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -152,9 +152,7 @@ VERSION
__kernel_sync_dicache_p5;
__kernel_sigtramp32;
__kernel_sigtramp_rt32;
-#ifdef CONFIG_PPC64
__kernel_getcpu;
-#endif
__kernel_time;
local: *;
--
2.13.3
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