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

[Simon Guo <wei.guo.simon@gmail.com>]

On Mon, Jul 18, 2016 at 11:28:30AM +1000, Cyril Bur wrote:
> On Sun, 17 Jul 2016 11:25:43 +0800
> 
> The aim of this patch is to ensure that pt_regs, fp_state and vr_state always
> hold a threads 'live' registers. So, after a recheckpoint fp_state is where the
> the state should be. tm_reclaim_thread() does a save_all() before doing the
> reclaim.
> 
> This means that the call to restore_math() is a replacement for all deleted
> lines above it.
> 
> I added it here because I'd prefer to be safe but I left that comment in
> because I suspect restore_math() will be called later and we can get away with
> not calling it 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?
> > 
> 
> I'm not sure what you mean by 'fresh'. You do highlight that we'll have to be
> sure that the MSR bits are off (so that restore_math() doesn't assume the
> registers are already loaded) which makes me think that tm_reclaim_thread()
> should be doing a giveup_all(), I'll fix that.
> 
> I hope that helps,
> 

Thanks Cyril. The explanation is detail and helpful.

- Simon