On Fri, 15 Jan 2016 17:25:26 +1100
Michael Neuling <mi...@neuling.org> wrote:
> On Fri, 2016-01-15 at 16:04 +1100, Cyril Bur wrote:
> > This patch adds the ability to be able to save the VSX registers to
> > the
> > thread struct without giving up (disabling the facility) next time
> > the
> > process returns to userspace.
> >
> > This patch builds on a previous optimisation for the FPU and VEC
> > registers
> > in the thread copy path to avoid a possibly pointless reload of VSX
> > state.
> >
> > Signed-off-by: Cyril Bur <cyril...@gmail.com>
> > ---
> > arch/powerpc/include/asm/switch_to.h | 1 -
> > arch/powerpc/kernel/ppc_ksyms.c | 4 ----
> > arch/powerpc/kernel/process.c | 23 ++++++++++++++++++-----
> > arch/powerpc/kernel/vector.S | 17 -----------------
> > 4 files changed, 18 insertions(+), 27 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/switch_to.h
> > b/arch/powerpc/include/asm/switch_to.h
> > index 29dda9d..4dfcd3e 100644
> > --- a/arch/powerpc/include/asm/switch_to.h
> > +++ b/arch/powerpc/include/asm/switch_to.h
> > @@ -52,7 +52,6 @@ static inline void disable_kernel_altivec(void)
> > extern void enable_kernel_vsx(void);
> > extern void flush_vsx_to_thread(struct task_struct *);
> > extern void giveup_vsx(struct task_struct *);
> > -extern void __giveup_vsx(struct task_struct *);
> > static inline void disable_kernel_vsx(void)
> > {
> > msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
> > diff --git a/arch/powerpc/kernel/ppc_ksyms.c
> > b/arch/powerpc/kernel/ppc_ksyms.c
> > index 41e1607..ef7024da 100644
> > --- a/arch/powerpc/kernel/ppc_ksyms.c
> > +++ b/arch/powerpc/kernel/ppc_ksyms.c
> > @@ -28,10 +28,6 @@ EXPORT_SYMBOL(load_vr_state);
> > EXPORT_SYMBOL(store_vr_state);
> > #endif
> >
> > -#ifdef CONFIG_VSX
> > -EXPORT_SYMBOL_GPL(__giveup_vsx);
> > -#endif
> > -
> > #ifdef CONFIG_EPAPR_PARAVIRT
> > EXPORT_SYMBOL(epapr_hypercall_start);
> > #endif
> > diff --git a/arch/powerpc/kernel/process.c
> > b/arch/powerpc/kernel/process.c
> > index 5566c32..3d907b8 100644
> > --- a/arch/powerpc/kernel/process.c
> > +++ b/arch/powerpc/kernel/process.c
> > @@ -252,20 +252,33 @@ EXPORT_SYMBOL_GPL(flush_altivec_to_thread);
> > #endif /* CONFIG_ALTIVEC */
> >
> > #ifdef CONFIG_VSX
> > -void giveup_vsx(struct task_struct *tsk)
> > +void __giveup_vsx(struct task_struct *tsk)
> > {
> > - check_if_tm_restore_required(tsk);
> > -
> > - msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
> > if (tsk->thread.regs->msr & MSR_FP)
> > __giveup_fpu(tsk);
> > if (tsk->thread.regs->msr & MSR_VEC)
> > __giveup_altivec(tsk);
> > + tsk->thread.regs->msr &= ~MSR_VSX;
> > +}
> > +
> > +void giveup_vsx(struct task_struct *tsk)
> > +{
> > + check_if_tm_restore_required(tsk);
> > +
> > + msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
> > __giveup_vsx(tsk);
> > msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
> > }
> > EXPORT_SYMBOL(giveup_vsx);
> >
> > +void save_vsx(struct task_struct *tsk)
> > +{
> > + if (tsk->thread.regs->msr & MSR_FP)
> > + save_fpu(tsk);
> > + if (tsk->thread.regs->msr & MSR_VEC)
> > + save_altivec(tsk);
> > +}
> > +
> > void enable_kernel_vsx(void)
> > {
> > WARN_ON(preemptible());
> > @@ -465,7 +478,7 @@ void save_all(struct task_struct *tsk)
> > #endif
> > #ifdef CONFIG_VSX
> > if (usermsr & MSR_VSX)
> > - __giveup_vsx(tsk);
> > + save_vsx(tsk);
>
> This seems suboptimal. save_vsx() will call save_fpu() and
> save_altivec() again, which you just called earlier in save_all().
>
Ah yes, will fix
> save_vsx() is only used here, so could be static.
>
Thanks.
> Also, put the #ifdef junk as part of the function so that the caller
> doesn't have to deal with it.
>
Can do absolutely, however this means that in save_all I can't check if the
function needs to be called or not. For example, without CONFIG_VSX, MSR_VSX
won't exist which means we might end up calling save_vsx THEN checking MSR_VSX
and returning early.
I'm happy to defer to you and mpe on what's nicer, I would side with avoiding
the function call at the cost of ugly #ifdefs but I can always see the merits
of clean code.
Thanks for the review,
Cyril
> Mikey
>
> > #endif
> > #ifdef CONFIG_SPE
> > if (usermsr & MSR_SPE)
> > diff --git a/arch/powerpc/kernel/vector.S
> > b/arch/powerpc/kernel/vector.S
> > index 51b0c17..1c2e7a3 100644
> > --- a/arch/powerpc/kernel/vector.S
> > +++ b/arch/powerpc/kernel/vector.S
> > @@ -151,23 +151,6 @@ _GLOBAL(load_up_vsx)
> > std r12,_MSR(r1)
> > b fast_exception_return
> >
> > -/*
> > - * __giveup_vsx(tsk)
> > - * Disable VSX for the task given as the argument.
> > - * Does NOT save vsx registers.
> > - */
> > -_GLOBAL(__giveup_vsx)
> > - addi r3,r3,THREAD /* want THREAD of
> > task */
> > - ld r5,PT_REGS(r3)
> > - cmpdi 0,r5,0
> > - beq 1f
> > - ld r4,_MSR-STACK_FRAME_OVERHEAD(r5)
> > - lis r3,MSR_VSX@h
> > - andc r4,r4,r3 /* disable VSX for
> > previous task */
> > - std r4,_MSR-STACK_FRAME_OVERHEAD(r5)
> > -1:
> > - blr
> > -
> > #endif /* CONFIG_VSX */
> >
> >
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