[PATCH 02/14] powerpc/64: syscall avoid restore_math call if possible
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2017-06-02 07:40:05
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
The syscall exit code that branches to restore_math is quite heavyweight on Book3S, consisting of 2 mtmsr instructions. This case can happen even if restore_math decides there is nothing to do due to lazy math restore. Check for lazy restore before calling restore_math. Move most of that case out of line. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/entry_64.S | 62 +++++++++++++++++++++++++++++------------- arch/powerpc/kernel/process.c | 4 +++ 2 files changed, 47 insertions(+), 19 deletions(-)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index bfbad08a1207..019a6322b982 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S@@ -210,27 +210,17 @@ system_call: /* label this so stack traces look sane */ andi. r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK) bne- syscall_exit_work - andi. r0,r8,MSR_FP - beq 2f + /* If MSR_FP and MSR_VEC are set in user msr, then no need to restore */ + li r0,MSR_FP #ifdef CONFIG_ALTIVEC - andis. r0,r8,MSR_VEC@h - bne 3f + oris r0,r0,MSR_VEC@h #endif -2: addi r3,r1,STACK_FRAME_OVERHEAD -#ifdef CONFIG_PPC_BOOK3S - li r10,MSR_RI - mtmsrd r10,1 /* Restore RI */ -#endif - bl restore_math -#ifdef CONFIG_PPC_BOOK3S - li r11,0 - mtmsrd r11,1 -#endif - ld r8,_MSR(r1) - ld r3,RESULT(r1) - li r11,-MAX_ERRNO + andc r7,r8,r0 + cmpd r7,r0 + bne syscall_restore_math +.Lsyscall_restore_math_cont: -3: cmpld r3,r11 + cmpld r3,r11 ld r5,_CCR(r1) bge- syscall_error .Lsyscall_error_cont:
@@ -263,7 +253,41 @@ syscall_error: neg r3,r3 std r5,_CCR(r1) b .Lsyscall_error_cont - + +syscall_restore_math: + /* + * Some initial tests from restore_math to avoid the heavyweight + * C code entry and MSR manipulations. + */ + LOAD_REG_IMMEDIATE(r0, MSR_TS_MASK) + and. r0,r0,r8 + bne 1f + + ld r7,PACACURRENT(r13) + lbz r0,THREAD+THREAD_LOAD_FP(r7) +#ifdef CONFIG_ALTIVEC + lbz r6,THREAD+THREAD_LOAD_VEC(r7) + add r0,r0,r6 +#endif + cmpdi r0,0 + beq .Lsyscall_restore_math_cont + +1: addi r3,r1,STACK_FRAME_OVERHEAD +#ifdef CONFIG_PPC_BOOK3S + li r10,MSR_RI + mtmsrd r10,1 /* Restore RI */ +#endif + bl restore_math +#ifdef CONFIG_PPC_BOOK3S + li r11,0 + mtmsrd r11,1 +#endif + /* Restore volatiles, reload MSR from updated one */ + ld r8,_MSR(r1) + ld r3,RESULT(r1) + li r11,-MAX_ERRNO + b .Lsyscall_restore_math_cont + /* Traced system call support */ syscall_dotrace: bl save_nvgprs
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index baae104b16c7..5cbb8b1faf7e 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c@@ -511,6 +511,10 @@ void restore_math(struct pt_regs *regs) { unsigned long msr; + /* + * Syscall exit makes a similar initial check before branching + * to restore_math. Keep them in synch. + */ if (!msr_tm_active(regs->msr) && !current->thread.load_fp && !loadvec(current->thread)) return;
--
2.11.0