On Mon, 2017-05-08 at 17:16 +1000, Michael Neuling wrote: > In this commit: > commit dc3106690b20305c3df06b42456fe386dd632ac9 > Author: Cyril Bur <[email protected]> > powerpc: tm: Always use fp_state and vr_state to store live registers > > A section of code was removed that copied the current state to > checkpointed state. This should not have been removed. >
-[space] > When an FP unavailable is taken inside a transaction, we need to abort > the transaction. This is because at the time of the tbegin, the FP > state is bogus so the state stored in the checkpointed registers is > incorrect. To fix this, we treclaim (to get the checkpointed GPRs) and > then copy the thread_struct FP live state into the checkpointed > state. We then trecheckpoint so that the FP state is correctly > restored into the CPU. > > The coping of the FP registers from live to checkpointed is what was > missing. > > This simplifies the logic slightly from the original patch. > tm_reclaim_thread() will now always write the checkpointed FP > state. Either the checkpointed FP statte will be written as part of state > the actual treclaim (in tm.S), or it'll be a copy of the live > state. Which one we use is based on MSR[FP] from userspace. > > Similarly for VMX. > > CC: <[email protected]> # 4.9+ > Signed-off-by: Michael Neuling <[email protected]> Reviewed-by: [email protected] > --- > arch/powerpc/kernel/process.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index d645da302b..6305353237 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -864,6 +864,25 @@ static void tm_reclaim_thread(struct thread_struct *thr, > if (!MSR_TM_SUSPENDED(mfmsr())) > return; > > + /* > + * If we are in a transaction and FP is off then we can't have > + * used FP inside that transaction. Hence the checkpointed > + * state is the same as the live state. We need to copy the > + * live state to the checkpointed state so that when the > + * transaction is restored, the checkpointed state is correct > + * and the aborted transaction sees the correct state. We use -[space] > + * ckpt_regs.msr here as that's what tm_reclaim will use to > + * determine if it's going to write the checkpointed state or > + * not. So either this will write the checkpointed registers, > + * or reclaim will. Similarly for VMX. -[space] > + */ > + if ((thr->ckpt_regs.msr & MSR_FP) == 0) > + memcpy(&thr->ckfp_state, &thr->fp_state, > + sizeof(struct thread_fp_state)); > + if ((thr->ckpt_regs.msr & MSR_VEC) == 0) > + memcpy(&thr->ckvr_state, &thr->vr_state, > + sizeof(struct thread_vr_state)); > + > giveup_all(container_of(thr, struct task_struct, thread)); > > tm_reclaim(thr, thr->ckpt_regs.msr, cause);
