Messages in this thread Patch in this message |  | | Subject | Re: [PATCH v5 17/22] powerpc/syscall: Do not check unsupported scv vector on PPC32 | From | Christophe Leroy <> | Date | Tue, 9 Feb 2021 07:13:17 +0100 |
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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.leroy@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 >> >>
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