On Tue, 9 Jul 2024 at 09:58, Alexandru Elisei <alexandru.elisei@xxxxxxx> 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@xxxxxxxxxx>
> > Cc: Anders Roxell <anders.roxell@xxxxxxxxxx>
> > ---
> > 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)?
When we're using TCG but not icount mode we present only the SW_INCR,
CPU_CYCLES, STALL_FRONTEND, STALL_BACKEND and STALL events.
If we aren't counting instructions we can't present an INST_RETIRED
event, because we don't have the information. (The STALL events
always return a zero count.)
thanks
-- PMM
