On Tue, Jan 31, 2023 at 09:52:56AM +0000, Alexandru Elisei wrote:
> Hi Drew,
>
> On Tue, Jan 31, 2023 at 07:56:23AM +0100, Andrew Jones wrote:
> > On Fri, Jan 27, 2023 at 05:59:16PM +0000, Alexandru Elisei wrote:
> > > From: Nikita Venkatesh <Nikita.Venkatesh@xxxxxxx>
> > >
> > > The test uses the following method.
> > >
> > > The primary CPU brings up all the secondary CPUs, which are held in a wait
> > > loop. Once the primary releases the CPUs, each of the secondary CPUs
> > > proceed to issue CPU_OFF.
> > >
> > > The primary CPU then checks for the status of the individual CPU_OFF
> > > request. There is a chance that some CPUs might return from the CPU_OFF
> > > function call after the primary CPU has finished the scan. There is no
> > > foolproof method to handle this, but the test tries its best to
> > > eliminate these false positives by introducing an extra delay if all the
> > > CPUs are reported offline after the initial scan.
> > >
> > > Signed-off-by: Nikita Venkatesh <Nikita.Venkatesh@xxxxxxx>
> > > [ Alex E: Skip CPU_OFF test if CPU_ON failed, drop cpu_off_success in
> > > favour of checking AFFINITY_INFO, commit message tweaking ]
> > > Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> > > ---
> > >
> > > Decided to drop Drew's Reviewed-by tag because the changes are not trivial
> > > from the previous version.
> > >
> > > arm/psci.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++----
> > > 1 file changed, 75 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/arm/psci.c b/arm/psci.c
> > > index f7238f8e0bbd..7034d8ebe6e1 100644
> > > --- a/arm/psci.c
> > > +++ b/arm/psci.c
> > > @@ -72,8 +72,9 @@ static bool psci_affinity_info_off(void)
> > > }
> > >
> > > static int cpu_on_ret[NR_CPUS];
> > > -static cpumask_t cpu_on_ready, cpu_on_done;
> > > +static cpumask_t cpu_on_ready, cpu_on_done, cpu_off_done;
> > > static volatile int cpu_on_start;
> > > +static volatile int cpu_off_start;
> > >
> > > extern void secondary_entry(void);
> > > static void cpu_on_do_wake_target(void)
> > > @@ -171,9 +172,71 @@ static bool psci_cpu_on_test(void)
> > > return !failed;
> > > }
> > >
> > > -int main(void)
> > > +static void cpu_off_secondary_entry(void *data)
> > > +{
> > > + int cpu = smp_processor_id();
> > > +
> > > + while (!cpu_off_start)
> > > + cpu_relax();
> > > + cpumask_set_cpu(cpu, &cpu_off_done);
> > > + cpu_psci_cpu_die();
> > > +}
> > > +
> > > +static bool psci_cpu_off_test(void)
> > > +{
> > > + bool failed = false;
> > > + int i, count, cpu;
> > > +
> > > + for_each_present_cpu(cpu) {
> > > + if (cpu == 0)
> > > + continue;
> > > + on_cpu_async(cpu, cpu_off_secondary_entry, NULL);
> > > + }
> > > +
> > > + cpumask_set_cpu(0, &cpu_off_done);
> > > +
> > > + cpu_off_start = 1;
> > > + report_info("waiting for the CPUs to be offlined...");
> > > + while (!cpumask_full(&cpu_off_done))
> > > + cpu_relax();
> > > +
> > > + /* Allow all the other CPUs to complete the operation */
> > > + for (i = 0; i < 100; i++) {
> > > + mdelay(10);
> > > +
> > > + count = 0;
> > > + for_each_present_cpu(cpu) {
> > > + if (cpu == 0)
> > > + continue;
> > > + if (psci_affinity_info(cpus[cpu], 0) != PSCI_0_2_AFFINITY_LEVEL_OFF)
> > > + count++;
> > > + }
> > > + if (count > 0)
> > > + continue;
> >
> > This should be
> >
> > if (count == 0)
> > break;
> >
> > otherwise we never leave the loop early.
>
> Duh, don't know what I was thinking. Thanks for noticing it.
>
> >
> > > + }
> > > +
> > > + /* Try to catch CPUs that return from CPU_OFF. */
> > > + if (count == 0)
> > > + mdelay(100);
> > > +
> > > + for_each_present_cpu(cpu) {
> > > + if (cpu == 0)
> > > + continue;
> > > + if (cpu_idle(cpu)) {
> > > + report_info("CPU%d failed to be offlined", cpu);
> > > + if (psci_affinity_info(cpus[cpu], 0) == PSCI_0_2_AFFINITY_LEVEL_OFF)
> > > + report_info("AFFINITY_INFO incorrectly reports CPU%d as offline", cpu);
> > > + failed = true;
> > > + }
> > > + }
> > > +
> > > + return !failed;
> > > +}
> > > +
> > > +int main(int argc, char **argv)
I just noticed we're adding argc,argv in this patch, but not using them.
> > > {
> > > int ver = psci_invoke(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
> > > + bool cpu_on_success = true;
> > >
> > > report_prefix_push("psci");
> > >
> > > @@ -188,10 +251,17 @@ int main(void)
> > > report(psci_affinity_info_on(), "affinity-info-on");
> > > report(psci_affinity_info_off(), "affinity-info-off");
> > >
> > > - if (ERRATA(6c7a5dce22b3))
> > > - report(psci_cpu_on_test(), "cpu-on");
> > > - else
> > > + if (ERRATA(6c7a5dce22b3)) {
> > > + cpu_on_success = psci_cpu_on_test();
> > > + report(cpu_on_success, "cpu-on");
> > > + } else {
> > > report_skip("Skipping unsafe cpu-on test. Set ERRATA_6c7a5dce22b3=y to enable.");
> > > + }
> > > +
> > > + if (!cpu_on_success)
> > > + report_skip("Skipping cpu-off test because the cpu-on test failed");
> >
> > We should output "was skipped" when the cpu-on test was skipped, rather
> > than always reporting "failed". We need two booleans, try_cpu_on_test and
> > cpu_on_success.
>
> This is not about cpu-on being a precondition for cpu-off. cpu-off makes
> only one assumption, and that is that all secondaries can be onlined
> successfully. Even if cpu-on is never run, cpu-off calls on_cpu_async,
> which will online a secondary. This is safe even if the errata is not
> present, because the errata is about concurrent CPU_ON calls for the same
> VCPU, not for different VCPUs.
>
> The cpu-off test is skipped here because it can hang indefinitely if
> onlining CPU1 was not successful:
>
> [..]
> for_each_present_cpu(cpu) {
> if (cpu == 0)
> continue;
> on_cpu_async(cpu, cpu_off_secondary_entry, NULL);
> }
>
> cpumask_set_cpu(0, &cpu_off_done);
>
> cpu_off_start = 1;
> report_info("waiting for the CPUs to be offlined...");
> while (!cpumask_full(&cpu_off_done)) // infinite loop if CPU1
> cpu_relax(); // cannot be onlined.
>
> Does that make sense? Should I add a comment to make it clear why cpu-off
> is skipped when cpu-on fails?
I missed that cpu_on_success was initialized to true. Seeing that now, I
understand how the only time it's false is if the cpu-on test failed. When
I thought it was initialized to false it had two ways to be false, failure
or skip. I think it's a bit confusing to set a 'success' variable to true
when the test is skipped. Also, we can relax the condition as to whether
or not we try cpu-off by simply checking that all cpus, other than cpu0,
are in idle. How about
if (ERRATA(6c7a5dce22b3))
report(psci_cpu_on_test(), "cpu-on");
else
report_skip("Skipping unsafe cpu-on test. Set ERRATA_6c7a5dce22b3=y to enable.");
assert(!cpu_idle(0));
if (!ERRATA(6c7a5dce22b3) || cpumask_weight(&cpu_idle_mask) == nr_cpus - 1)
report(psci_cpu_off_test(), "cpu-off");
else
report_skip("Skipping cpu-off test because the cpu-on test failed");
Thanks,
drew
>
> Thanks,
> Alex
>
> >
> > > + else
> > > + report(psci_cpu_off_test(), "cpu-off");
> > >
> > > done:
> > > #if 0
> > > --
> > > 2.39.0
> > >
> >
> > Thanks,
> > drew
