Messages in this thread | | | Date | Fri, 27 Sep 2013 21:20:04 +0800 | From | Jiang Liu <> | Subject | Re: [RFT PATCH v1 2/7] arm64: restore FPSIMD to default state for kernel and signal contexts |
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On 09/27/2013 07:35 PM, Catalin Marinas wrote: > On Fri, Sep 27, 2013 at 09:04:42AM +0100, Jiang Liu wrote: >> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c >> index bb785d2..12a25e5 100644 >> --- a/arch/arm64/kernel/fpsimd.c >> +++ b/arch/arm64/kernel/fpsimd.c >> @@ -80,9 +80,14 @@ void fpsimd_thread_switch(struct task_struct *next) >> >> void fpsimd_flush_thread(void) >> { >> + struct fpsimd_state *state = ¤t->thread.fpsimd_state; >> + >> preempt_disable(); >> - memset(¤t->thread.fpsimd_state, 0, sizeof(struct fpsimd_state)); >> - fpsimd_load_state(¤t->thread.fpsimd_state); >> + memset(state, 0, sizeof(struct fpsimd_state)); >> +#if (AARCH64_FPCR_DEFAULT_VAL != 0) >> + state->fpcr = AARCH64_FPCR_DEFAULT_VAL; >> +#endif >> + fpsimd_load_state(state); >> preempt_enable(); > > We can leave this to 0 as the default for user. Glibc already programs > this register. OK, will drop it.
> >> } >> >> @@ -99,6 +104,8 @@ void kernel_neon_begin(void) >> >> if (current->mm) >> fpsimd_save_state(¤t->thread.fpsimd_state); >> + >> + fpsimd_init_hw_state(); > > This function should indeed do some initialisation rather than relying > on whatever the user set for FPCR. > >> diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c >> index 890a591..6d80612 100644 >> --- a/arch/arm64/kernel/signal.c >> +++ b/arch/arm64/kernel/signal.c >> @@ -52,6 +52,7 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx) >> >> /* dump the hardware registers to the fpsimd_state structure */ >> fpsimd_save_state(fpsimd); >> + fpsimd_init_hw_state(); > > Here I think we need to leave the default user setting for fpcr as > decided by glibc (or libgcc) when an application starts. OK, will keep FPCR and clear FPSR.
> >> /* copy the FP and status/control registers */ >> err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs)); >> diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c >> index e393174..cb2cb41 100644 >> --- a/arch/arm64/kernel/signal32.c >> +++ b/arch/arm64/kernel/signal32.c >> @@ -248,6 +248,7 @@ static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame) >> * in AArch32. >> */ >> fpsimd_save_state(fpsimd); >> + fpsimd_init_hw_state(); > > Same here. >
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