On Tue, 2018-02-20 at 13:50 +1100, Michael Neuling wrote:
> On Tue, 2018-02-20 at 11:22 +1100, Cyril Bur wrote:
>
>
> The comment from the cover sheet should be here
>
> > ---
> > arch/powerpc/include/asm/exception-64s.h | 25 +++++++++++++++++++++
> > arch/powerpc/kernel/entry_64.S | 5 +++++
> > arch/powerpc/kernel/process.c | 37
> > ++++++++++++++++++++++++++++----
> > 3 files changed, 63 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/exception-64s.h
> > b/arch/powerpc/include/asm/exception-64s.h
> > index 471b2274fbeb..f904f19a9ec2 100644
> > --- a/arch/powerpc/include/asm/exception-64s.h
> > +++ b/arch/powerpc/include/asm/exception-64s.h
> > @@ -35,6 +35,7 @@
> > * implementations as possible.
> > */
> > #include <asm/head-64.h>
> > +#include <asm/tm.h>
> >
> > /* PACA save area offsets (exgen, exmc, etc) */
> > #define EX_R9 0
> > @@ -127,6 +128,26 @@
> > hrfid; \
> > b hrfi_flush_fallback
> >
> > +#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> > +#define TM_KERNEL_ENTRY
> > \
> > + ld r3,_MSR(r1); \
> > + /* Probably don't need to check if coming from user/kernel */ \
> > + /* If TM is suspended or active then we must have come from*/ \
> > + /* userspace */ \
> > + andi. r0,r3,MSR_PR; \
> > + beq 1f; \
> > + rldicl. r3,r3,(64-MSR_TS_LG),(64-2); /* SUSPENDED or ACTIVE*/ \
> > + beql+ 1f; /* Not SUSPENDED or ACTIVE */ \
> > + bl save_nvgprs; \
> > + RECONCILE_IRQ_STATE(r10,r11); \
> > + li r3,TM_CAUSE_MISC; \
> > + bl tm_reclaim_current; /* uint8 cause */ \
> > +1:
> > +
> > +#else /* CONFIG_PPC_TRANSACTIONAL_MEM */
> > +#define TM_KERNEL_ENTRY
> > +#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
> > +
> > #ifdef CONFIG_RELOCATABLE
> > #define __EXCEPTION_RELON_PROLOG_PSERIES_1(label, h)
> > \
> > mfspr r11,SPRN_##h##SRR0; /* save SRR0 */ \
> > @@ -675,6 +696,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
> > EXCEPTION_PROLOG_COMMON(trap, area); \
> > /* Volatile regs are potentially clobbered here */ \
> > additions; \
> > + /* This is going to need to go somewhere else as well */\
> > + /* See comment in tm_recheckpoint() */\
> > + TM_KERNEL_ENTRY; \
> > addi r3,r1,STACK_FRAME_OVERHEAD; \
> > bl hdlr; \
> > b ret
> > @@ -689,6 +713,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
> > EXCEPTION_PROLOG_COMMON_3(trap); \
> > /* Volatile regs are potentially clobbered here */ \
> > additions; \
> > + TM_KERNEL_ENTRY; \
> > addi r3,r1,STACK_FRAME_OVERHEAD; \
> > bl hdlr
> >
> > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> > index 2cb5109a7ea3..107c15c6f48b 100644
> > --- a/arch/powerpc/kernel/entry_64.S
> > +++ b/arch/powerpc/kernel/entry_64.S
> > @@ -126,6 +126,11 @@ BEGIN_FW_FTR_SECTION
> > 33:
> > END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
> > #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE && CONFIG_PPC_SPLPAR */
> > + TM_KERNEL_ENTRY
> > + REST_GPR(0,r1)
> > + REST_4GPRS(3,r1)
> > + REST_2GPRS(7,r1)
> > + addi r9,r1,STACK_FRAME_OVERHEAD
>
> Why are we doing these restores here now?
The syscall handler expects the syscall params to still be in their
respective regs.
>
> >
> > /*
> > * A syscall should always be called with interrupts enabled
> > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> > index 77dc6d8288eb..ea75da0fd506 100644
> > --- a/arch/powerpc/kernel/process.c
> > +++ b/arch/powerpc/kernel/process.c
> > @@ -951,6 +951,23 @@ void tm_recheckpoint(struct thread_struct *thread)
> > if (!(thread->regs->msr & MSR_TM))
> > return;
> >
> > + /*
> > + * This is 'that' comment.
>
> I think I'm in the loop here but I don't actually know what this means.
>
> Senior Mikey moment or Crazy Cyril comments? I'll let the peanut gallery
> decide.
>
Oh quite possibly crazy Cyril comment that will have to be...
normalised. I should actually delete this and see if that's still the
case.
> > + *
> > + * If we get where with tm suspended or active then something
>
> s/where/here/
>
> > + * has gone wrong. I've added this now as a proof of concept.
> > + *
> > + * The problem I'm seeing without it is an attempt to
> > + * recheckpoint a CPU without a previous reclaim.
> > + *
> > + * I'm probably missed an exception entry with the
> > + * TM_KERNEL_ENTRY macro. Should be easy enough to find.
> > + */
> > + if (MSR_TM_ACTIVE(mfmsr()))
> > + return;
>
> I don't really get this. Wouldn't this test apply now?
>
> > +
> > + tm_enable();
>
> Why did we add this?
>
Ah yes that was a cleanup I noticed along the way and clearly forgot to
finish.
At the moment there's a bunch of tm_enable()s either before calling
functions like tm_recheckpoint() or tm_reclaim_current() or inside
helpers (tm_reclaim_current() for example again). I feel like callers
shouldn't have to worry, it should be up to the function actually doing
the TM work to enable it.
> > +
> > /* We really can't be interrupted here as the TEXASR registers can't
> > * change and later in the trecheckpoint code, we have a userspace R1.
> > * So let's hard disable over this region.
> > @@ -1009,6 +1026,13 @@ static inline void tm_recheckpoint_new_task(struct
> > task_struct *new)
> > static inline void __switch_to_tm(struct task_struct *prev,
> > struct task_struct *new)
> > {
> > + /*
> > + * So, with the rework none of this code should not be needed.
> > + * I've left in the reclaim for now. This *should* save us
> > + * from any mistake in the new code. Also the
> > + * enabling/disabling logic of MSR_TM really should be
> > + * refactored into a common way with MSR_{FP,VEC,VSX}
> > + */
> > if (cpu_has_feature(CPU_FTR_TM)) {
> > if (tm_enabled(prev) || tm_enabled(new))
> > tm_enable();
> > @@ -1016,11 +1040,14 @@ static inline void __switch_to_tm(struct
> > task_struct *prev,
> > if (tm_enabled(prev)) {
> > prev->thread.load_tm++;
> > tm_reclaim_task(prev);
> > - if (!MSR_TM_ACTIVE(prev->thread.regs->msr) &&
> > prev->thread.load_tm == 0)
> > - prev->thread.regs->msr &= ~MSR_TM;
> > + /*
> > + * The disabling logic may be confused don't
> > + * disable for now
> > + *
> > + * if (!MSR_TM_ACTIVE(prev->thread.regs->msr) &&
> > prev->thread.load_tm == 0)
> > + * prev->thread.regs->msr &= ~MSR_TM;
> > + */
>
> Why are you doing this when you just remove all this code in the next patch?
The next 3 or so patches will need squashing into this one before
merging.
> > }
> > -
> > - tm_recheckpoint_new_task(new);
> > }
> > }
> >
> > @@ -1055,6 +1082,8 @@ void restore_tm_state(struct pt_regs *regs)
> > msr_diff = current->thread.ckpt_regs.msr & ~regs->msr;
> > msr_diff &= MSR_FP | MSR_VEC | MSR_VSX;
> >
> > + tm_recheckpoint(¤t->thread);
> > +
>
> So why do we do tm_recheckpoint at all? Shouldn't most of the tm_blah code go
> away in process.c after all this?
>
I'm not sure I follow, we need to recheckpoint because we're going back
to userspace? Or would you rather calling the tm.S code directly from
the exception return path?
Yes, I hope we'll be able to have a fairly big cleanup commit of tm_
code in process.c at the end of this series.
> > /* Ensure that restore_math() will restore */
> > if (msr_diff & MSR_FP)
> > current->thread.load_fp = 1;
