Le 09/02/2021 à 03:00, Nicholas Piggin a écrit :
Excerpts from Christophe Leroy's message of February 9, 2021 1:10 am:
Only PPC64 has scv. No need to check the 0x7ff0 trap on PPC32.
For that, add a helper trap_is_unsupported_scv() similar to
trap_is_scv().
And ignore the scv parameter in syscall_exit_prepare (Save 14 cycles
346 => 332 cycles)
Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
v5: Added a helper trap_is_unsupported_scv()
---
arch/powerpc/include/asm/ptrace.h | 5 +++++
arch/powerpc/kernel/entry_32.S | 1 -
arch/powerpc/kernel/interrupt.c | 7 +++++--
3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/ptrace.h
b/arch/powerpc/include/asm/ptrace.h
index 58f9dc060a7b..2c842b11a924 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -229,6 +229,11 @@ static inline bool trap_is_scv(struct pt_regs *regs)
return (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && TRAP(regs) == 0x3000);
}
+static inline bool trap_is_unsupported_scv(struct pt_regs *regs)
+{
+ return (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && TRAP(regs) == 0x7ff0);
+}
This change is good.
+
static inline bool trap_is_syscall(struct pt_regs *regs)
{
return (trap_is_scv(regs) || TRAP(regs) == 0xc00);
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index cffe58e63356..7c824e8928d0 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -344,7 +344,6 @@ transfer_to_syscall:
ret_from_syscall:
addi r4,r1,STACK_FRAME_OVERHEAD
- li r5,0
bl syscall_exit_prepare
For this one, I think it would be nice to do the "right" thing and make
the function prototypes different on !64S. They could then declare a
local const bool scv = 0.
We could have syscall_exit_prepare and syscall_exit_prepare_maybe_scv
or something like that, 64s can use the latter one and the former can be
a wrapper that passes constant 0 for scv. Then we don't have different
prototypes for the same function, but you just have to make the 32-bit
version static inline and the 64-bit version exported to asm.
You can't call a static inline function from ASM, I don't understand you.
What is wrong for you really here ? Is that the fact we leave scv random, or is that the below
IS_ENABLED() ?
I don't mind keeping the 'li r5,0' before calling the function if you find it cleaner, the real
performance gain is with setting scv to 0 below for PPC32 (and maybe it should be set to zero for
book3e/64 too ?).
Other solution would be to do replace (!scv) by (!scv || !IS_ENABLED(CONFIG_PPC_BOOK3S_64)) in the
two places it is used in syscall_exit_prepare().
Any preference ?
Thanks
Christophe
@@ -224,6 +224,9 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
unsigned long ti_flags;
unsigned long ret = 0;
+ if (IS_ENABLED(CONFIG_PPC32))
+ scv = 0;
+
CT_WARN_ON(ct_state() == CONTEXT_USER);
#ifdef CONFIG_PPC64
--
2.25.0
