Re: [kvm-unit-tests PATCH v1 1/2] arm/pmu: skip the PMU introspection test if missing

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Tue, 9 Jul 2024 at 09:58, Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>>
>> Hi,
>>
>> On Tue, Jul 02, 2024 at 05:35:14PM +0100, Alex Bennée wrote:
>> > The test for number of events is not a substitute for properly
>> > checking the feature register. Fix the define and skip if PMUv3 is not
>> > available on the system. This includes emulator such as QEMU which
>> > don't implement PMU counters as a matter of policy.
>> >
>> > Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> > Cc: Anders Roxell <anders.roxell@linaro.org>
>> > ---
>> >  arm/pmu.c | 7 ++++++-
>> >  1 file changed, 6 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/arm/pmu.c b/arm/pmu.c
>> > index 9ff7a301..66163a40 100644
>> > --- a/arm/pmu.c
>> > +++ b/arm/pmu.c
>> > @@ -200,7 +200,7 @@ static void test_overflow_interrupt(bool overflow_at_64bits) {}
>> >  #define ID_AA64DFR0_PERFMON_MASK  0xf
>> >
>> >  #define ID_DFR0_PMU_NOTIMPL  0b0000
>> > -#define ID_DFR0_PMU_V3               0b0001
>> > +#define ID_DFR0_PMU_V3               0b0011
>> >  #define ID_DFR0_PMU_V3_8_1   0b0100
>> >  #define ID_DFR0_PMU_V3_8_4   0b0101
>> >  #define ID_DFR0_PMU_V3_8_5   0b0110
>> > @@ -286,6 +286,11 @@ static void test_event_introspection(void)
>> >               return;
>> >       }
>> >
>> > +     if (pmu.version < ID_DFR0_PMU_V3) {
>> > +             report_skip("PMUv3 extensions not supported, skip ...");
>> > +             return;
>> > +     }
>> > +
>>
>> I don't get this patch - test_event_introspection() is only run on 64bit. On
>> arm64, if there is a PMU present, that PMU is a PMUv3.  A prerequisite to
>> running any PMU tests is for pmu_probe() to succeed, and pmu_probe() fails if
>> there is no PMU implemented (PMUVer is either 0, or 0b1111). As a result, if
>> test_event_introspection() is executed, then a PMUv3 is present.
>>
>> When does QEMU advertise FEAT_PMUv3*, but no event counters (other than the cycle
>> counter)?

The other option I have is this:

--8<---------------cut here---------------start------------->8---
arm/pmu: event-introspection needs icount for TCG

The TCG accelerator will report a PMU (unless explicitly disabled with
-cpu foo,pmu=off) however not all events are available unless you run
under icount. Fix this by splitting the test into a kvm and tcg
version.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

1 file changed, 8 insertions(+)
arm/unittests.cfg | 8 ++++++++

modified   arm/unittests.cfg
@@ -52,8 +52,16 @@ extra_params = -append 'cycle-counter 0'
 file = pmu.flat
 groups = pmu
 arch = arm64
+accel = kvm
 extra_params = -append 'pmu-event-introspection'
 
+[pmu-event-introspection-icount]
+file = pmu.flat
+groups = pmu
+arch = arm64
+accel = tcg
+extra_params = -icount shift=1 -append 'pmu-event-introspection'
+
 [pmu-event-counter-config]
 file = pmu.flat
 groups = pmu
--8<---------------cut here---------------end--------------->8---

which just punts icount on TCG to its own test (note there are commented
out versions further down the unitests.cfg file)

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro