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)
> > {
> > 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?
Thanks,
Alex
>
> > + else
> > + report(psci_cpu_off_test(), "cpu-off");
> >
> > done:
> > #if 0
> > --
> > 2.39.0
> >
>
> Thanks,
> drew
