On Nov 30 09:13, Richard Henderson wrote:
> On 11/20/18 1:26 PM, Aaron Lindsay wrote:
> > Setup a QEMUTimer to get a callback when we expect counters to next
> > overflow and trigger an interrupt at that time.
> >
> > Signed-off-by: Aaron Lindsay <alind...@codeaurora.org>
> > Signed-off-by: Aaron Lindsay <alind...@os.amperecomputing.com>
> > ---
> > target/arm/cpu.c | 12 +++++
> > target/arm/cpu.h | 7 +++
> > target/arm/helper.c | 126 +++++++++++++++++++++++++++++++++++++++++---
> > 3 files changed, 139 insertions(+), 6 deletions(-)
> >
> > diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> > index 208a08e867..7311a48e3c 100644
> > --- a/target/arm/cpu.c
> > +++ b/target/arm/cpu.c
> > @@ -827,6 +827,13 @@ static void arm_cpu_finalizefn(Object *obj)
> > QLIST_REMOVE(hook, node);
> > g_free(hook);
> > }
> > +#ifndef CONFIG_USER_ONLY
> > + if (arm_feature(&cpu->env, ARM_FEATURE_PMU) && cpu->pmu_timer) {
>
> No need for two tests here. Just check cpu->pmu_timer.
> (If it's set for any reason it should be freed, surely.)
>
> > @@ -1305,7 +1338,18 @@ void pmccntr_op_start(CPUARMState *env)
> > eff_cycles /= 64;
> > }
> >
> > - env->cp15.c15_ccnt = eff_cycles - env->cp15.c15_ccnt_delta;
> > + uint64_t new_pmccntr = eff_cycles - env->cp15.c15_ccnt_delta;
> > +
> > + unsigned int overflow_bit = (env->cp15.c9_pmcr & PMCRLC) ? 63 : 31;
> > + uint64_t overflow_mask = (uint64_t)1 << overflow_bit;
> > + if (!(new_pmccntr & overflow_mask) &&
> > + (env->cp15.c15_ccnt & overflow_mask)) {
>
> Fyi, this expression is
>
> env->cp15.c15_ccnt & ~new_pmccntr & overflow_mask
>
> > + env->cp15.c9_pmovsr |= (1 << 31);
> > + new_pmccntr &= ~overflow_mask;
>
> Why this line? You just checked that overflow_mask was unset in new_pmccntr
> above.
This ensures that when overflow_bit == 31 (because PMCR.LC is not set)
the high 32 bits remain 0 even after an overflow has occurred. As you
point out, it's silly when overflow_bit == 64, but I didn't think it was
worth the extra conditional to avoid it.
> > @@ -1318,13 +1362,28 @@ void pmccntr_op_start(CPUARMState *env)
> > void pmccntr_op_finish(CPUARMState *env)
> > {
> > if (pmu_counter_enabled(env, 31)) {
> > - uint64_t prev_cycles = env->cp15.c15_ccnt_delta;
> > +#ifndef CONFIG_USER_ONLY
> > + uint64_t delta;
> > + if (env->cp15.c9_pmcr & PMCRLC) {
> > + delta = UINT64_MAX - env->cp15.c15_ccnt + 1;
> > + } else {
> > + delta = UINT32_MAX - (uint32_t)env->cp15.c15_ccnt + 1;
> > + }
>
> FWIW, this is the same as
>
> delta = -env->cp15.c15_ccnt;
> if (!(env->cp15.c9_pmcr & PMCRLC)) {
> delta = (uint32_t)delta;
> }
Thanks for your review. I'll take a look at your suggested logic
simplifications for v9, do you think that this patch looks OK at the
big-picture level?
-Aaron
