This series:
- adds getcpu()
- adds coarse clocks in clock_gettime
- fixes and adds all clocks in clock_getres
- optimises the retrieval of the datapage address
- optimises the cache functions
It puts together the three patches sent out earlier allthought they
were not presented as a series, hence the 'v2' tag for now.
v2:
- Used named labels in patch 2
- Added patch from Vincenzo to fix clock_getres() (patch 3)
- Removed unnecessary label in patch 4 as suggested by Segher
- Added patches 5 to 8
Christophe Leroy (8):
powerpc/32: Add VDSO version of getcpu
powerpc/vdso32: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE
powerpc: Fix vDSO clock_getres()
powerpc/vdso32: inline __get_datapage()
powerpc/vdso32: Don't read cache line size from the datapage on PPC32.
powerpc/vdso32: use LOAD_REG_IMMEDIATE()
powerpc/vdso32: implement clock_getres entirely
powerpc/vdso32: miscellaneous optimisations
arch/powerpc/include/asm/vdso.h | 2 +
arch/powerpc/include/asm/vdso_datapage.h | 6 +-
arch/powerpc/kernel/asm-offsets.c | 7 +-
arch/powerpc/kernel/head_32.h | 13 ++++
arch/powerpc/kernel/head_booke.h | 11 +++
arch/powerpc/kernel/time.c | 1 +
arch/powerpc/kernel/vdso.c | 5 --
arch/powerpc/kernel/vdso32/Makefile | 4 +-
arch/powerpc/kernel/vdso32/cacheflush.S | 33 ++++++--
arch/powerpc/kernel/vdso32/datapage.S | 32 ++------
arch/powerpc/kernel/vdso32/datapage.h | 11 +++
arch/powerpc/kernel/vdso32/getcpu.S | 13 +++-
arch/powerpc/kernel/vdso32/gettimeofday.S | 125 +++++++++++++++++++++---------
arch/powerpc/kernel/vdso32/vdso32.lds.S | 2 -
arch/powerpc/kernel/vdso64/gettimeofday.S | 7 +-
15 files changed, 183 insertions(+), 89 deletions(-)
create mode 100644 arch/powerpc/kernel/vdso32/datapage.h
--
2.13.3
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 <[email protected]>
---
v2: fixed build error in getcpu.S
---
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..bde226ad904d 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
This is copied and adapted from commit 5c929885f1bb ("powerpc/vdso64:
Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE")
from Santosh Sivaraj <[email protected]>
Benchmark from vdsotest-all:
clock-gettime-realtime: syscall: 3601 nsec/call
clock-gettime-realtime: libc: 1072 nsec/call
clock-gettime-realtime: vdso: 931 nsec/call
clock-gettime-monotonic: syscall: 4034 nsec/call
clock-gettime-monotonic: libc: 1213 nsec/call
clock-gettime-monotonic: vdso: 1076 nsec/call
clock-gettime-realtime-coarse: syscall: 2722 nsec/call
clock-gettime-realtime-coarse: libc: 805 nsec/call
clock-gettime-realtime-coarse: vdso: 668 nsec/call
clock-gettime-monotonic-coarse: syscall: 2949 nsec/call
clock-gettime-monotonic-coarse: libc: 882 nsec/call
clock-gettime-monotonic-coarse: vdso: 745 nsec/call
Additional test passed with:
vdsotest -d 30 clock-gettime-monotonic-coarse verify
Signed-off-by: Christophe Leroy <[email protected]>
Cc: Naveen N. Rao <[email protected]>
Cc: Santosh Sivaraj <[email protected]>
Link: https://github.com/linuxppc/issues/issues/41
---
arch/powerpc/kernel/vdso32/gettimeofday.S | 64 +++++++++++++++++++++++++++----
1 file changed, 57 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index becd9f8767ed..decd263c16e0 100644
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
@@ -71,7 +71,13 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
cmpli cr0,r3,CLOCK_REALTIME
cmpli cr1,r3,CLOCK_MONOTONIC
cror cr0*4+eq,cr0*4+eq,cr1*4+eq
- bne cr0,99f
+
+ cmpli cr5,r3,CLOCK_REALTIME_COARSE
+ cmpli cr6,r3,CLOCK_MONOTONIC_COARSE
+ cror cr5*4+eq,cr5*4+eq,cr6*4+eq
+
+ cror cr0*4+eq,cr0*4+eq,cr5*4+eq
+ bne cr0, .Lgettime_fallback
mflr r12 /* r12 saves lr */
.cfi_register lr,r12
@@ -80,8 +86,10 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
mr r9,r3 /* datapage ptr in r9 */
lis r7,NSEC_PER_SEC@h /* want nanoseconds */
ori r7,r7,NSEC_PER_SEC@l
-50: bl __do_get_tspec@local /* get sec/nsec from tb & kernel */
- bne cr1,80f /* not monotonic -> all done */
+ beq cr5, .Lcoarse_clocks
+.Lprecise_clocks:
+ bl __do_get_tspec@local /* get sec/nsec from tb & kernel */
+ bne cr1, .Lfinish /* not monotonic -> all done */
/*
* CLOCK_MONOTONIC
@@ -105,12 +113,53 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
add r9,r9,r0
lwz r0,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
cmpl cr0,r8,r0 /* check if updated */
- bne- 50b
+ bne- .Lprecise_clocks
+ b .Lfinish_monotonic
+
+ /*
+ * For coarse clocks we get data directly from the vdso data page, so
+ * we don't need to call __do_get_tspec, but we still need to do the
+ * counter trick.
+ */
+.Lcoarse_clocks:
+ lwz r8,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
+ andi. r0,r8,1 /* pending update ? loop */
+ bne- .Lcoarse_clocks
+ add r9,r9,r0 /* r0 is already 0 */
+
+ /*
+ * CLOCK_REALTIME_COARSE, below values are needed for MONOTONIC_COARSE
+ * too
+ */
+ lwz r3,STAMP_XTIME+TSPC32_TV_SEC(r9)
+ lwz r4,STAMP_XTIME+TSPC32_TV_NSEC(r9)
+ bne cr6,1f
+
+ /* CLOCK_MONOTONIC_COARSE */
+ lwz r5,(WTOM_CLOCK_SEC+LOPART)(r9)
+ lwz r6,WTOM_CLOCK_NSEC(r9)
+
+ /* check if counter has updated */
+ or r0,r6,r5
+1: or r0,r0,r3
+ or r0,r0,r4
+ xor r0,r0,r0
+ add r3,r3,r0
+ lwz r0,CFG_TB_UPDATE_COUNT+LOPART(r9)
+ cmpl cr0,r0,r8 /* check if updated */
+ bne- .Lcoarse_clocks
+
+ /* Counter has not updated, so continue calculating proper values for
+ * sec and nsec if monotonic coarse, or just return with the proper
+ * values for realtime.
+ */
+ bne cr6, .Lfinish
/* Calculate and store result. Note that this mimics the C code,
* which may cause funny results if nsec goes negative... is that
* possible at all ?
*/
+.Lfinish_monotonic:
add r3,r3,r5
add r4,r4,r6
cmpw cr0,r4,r7
@@ -118,11 +167,12 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
blt 1f
subf r4,r7,r4
addi r3,r3,1
-1: bge cr1,80f
+1: bge cr1, .Lfinish
addi r3,r3,-1
add r4,r4,r7
-80: stw r3,TSPC32_TV_SEC(r11)
+.Lfinish:
+ stw r3,TSPC32_TV_SEC(r11)
stw r4,TSPC32_TV_NSEC(r11)
mtlr r12
@@ -133,7 +183,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
/*
* syscall fallback
*/
-99:
+.Lgettime_fallback:
li r0,__NR_clock_gettime
.cfi_restore lr
sc
--
2.13.3
Hi Christophe,
Sorry I'm late replying to this.
Christophe Leroy <[email protected]> writes:
> 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 <[email protected]>
>
> ---
> v2: fixed build error in getcpu.S
> ---
> 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
We are still in the middle of the years long process of removing the
"magic" syscall on 64-bit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kernel/exceptions-64s.S?commit=4d856f72c10ecb060868ed10ff1b1453943fc6c8#n1578
Can we not add another one on 32-bit?
Is it really such a fast path that it's worth putting a wart in the
syscall entry like that?
Is there some other method? On s390 they have a per-cpu VDSO page, that
would be a nice option. How we do that would be specific to a particular
MMU, and maybe not even possible with some MMUs. So maybe that's not
feasible.
If you do want to add a fastpath syscall then please just add it as a
regular syscall number, that way it's at least a bit less of a wart.
It's still not visible via tracing/ptrace etc. which is a pain but at
least the number is not "magical" too.
cheers
> /* 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..bde226ad904d 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
Le 18/09/2019 à 07:51, Michael Ellerman a écrit :
>
> We are still in the middle of the years long process of removing the
> "magic" syscall on 64-bit:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kernel/exceptions-64s.S?commit=4d856f72c10ecb060868ed10ff1b1453943fc6c8#n1578
>
>
> Can we not add another one on 32-bit?
>
> Is it really such a fast path that it's worth putting a wart in the
> syscall entry like that?
>
> Is there some other method? On s390 they have a per-cpu VDSO page, that
> would be a nice option. How we do that would be specific to a particular
> MMU, and maybe not even possible with some MMUs. So maybe that's not
> feasible.
Ok, for now I remove the fast syscall and only keep the VDSO getcpu()
for non SMP.
I think we may in the future implement a per-cpu VDSO page that will be
mapped to the process based on the CPU it is running on. I need to look
at that in more details.
Christophe