Re: [PATCH 3/5] powerpc: tm: Always use fp_state and vr_state to store live registers

[Simon Guo <simonguo@linux.vnet.ibm.com>]

Hi Cyril,
On Wed, Jun 08, 2016 at 02:00:34PM +1000, Cyril Bur wrote:
> @@ -917,24 +907,10 @@ static inline void tm_recheckpoint_new_task(struct task_struct *new)
>  		 "(new->msr 0x%lx, new->origmsr 0x%lx)\n",
>  		 new->pid, new->thread.regs->msr, msr);
>  
> -	/* This loads the checkpointed FP/VEC state, if used */
>  	tm_recheckpoint(&new->thread, msr);
>  
> -	/* This loads the speculative FP/VEC state, if used */
> -	if (msr & MSR_FP) {
> -		do_load_up_transact_fpu(&new->thread);
> -		new->thread.regs->msr |=
> -			(MSR_FP | new->thread.fpexc_mode);
> -	}
> -#ifdef CONFIG_ALTIVEC
> -	if (msr & MSR_VEC) {
> -		do_load_up_transact_altivec(&new->thread);
> -		new->thread.regs->msr |= MSR_VEC;
> -	}
> -#endif
> -	/* We may as well turn on VSX too since all the state is restored now */
> -	if (msr & MSR_VSX)
> -		new->thread.regs->msr |= MSR_VSX;
> +	/* Won't restore math get called later? */
> +	restore_math(new->thread.regs);

I have some question for the "restore_math" in tm_recheckpoint_new_task().

Per my understanding, now after tm_recheckpoint, the fp_state content
is obsolete.  However restore_math() will try to restore FP/Vec/VSX state 
from fp_state, (orginally it is right, since fp_state was the valid
checkpointed state and consistent with FP register ). Should we remove
the restore_math() here?

And, should the thread's MSR now set FP bit in tm_recheckpoint(), to 
indicate that FP register content is "fresh" in contrast to thread.fp_state?

Please correct me if I am wrong.

Thanks,
- Simon