Re: [PATCH 1/5] powerpc: Test MSR_FP and MSR_VEC when enabling/flushing VSX

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2017-08-16 at 16:01 +1000, Benjamin Herrenschmidt wrote:
> VSX uses a combination of the old vector registers, the old FP registers
> and new "second halves" of the FP registers.
> 
> Thus when we need to see the VSX state in the thread struct
> (flush_vsx_to_thread) or when we'll use the VSX in the kernel
> (enable_kernel_vsx) we need to ensure they are all flushed into
> the thread struct if either of them is individually enabled.
> 
> Unfortunately we only tested if the whole VSX was enabled, not
> if they were individually enabled.
> 
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

And CC stable.

> ---
>  arch/powerpc/kernel/process.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 9f3e2c932dcc..883216b4296a 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -362,7 +362,8 @@ void enable_kernel_vsx(void)
>  
>  	cpumsr = msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
>  
> -	if (current->thread.regs && (current->thread.regs->msr & MSR_VSX)) {
> +	if (current->thread.regs &&
> +	    (current->thread.regs->msr & (MSR_VSX|MSR_VEC|MSR_FP))) {
>  		check_if_tm_restore_required(current);
>  		/*
>  		 * If a thread has already been reclaimed then the
> @@ -386,7 +387,7 @@ void flush_vsx_to_thread(struct task_struct *tsk)
>  {
>  	if (tsk->thread.regs) {
>  		preempt_disable();
> -		if (tsk->thread.regs->msr & MSR_VSX) {
> +		if (tsk->thread.regs->msr & (MSR_VSX|MSR_VEC|MSR_FP)) {
>  			BUG_ON(tsk != current);
>  			giveup_vsx(tsk);
>  		}