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)?
If you want to be extra correct, you can add the above check to pmu_probe() for
32bit, since I doubt that the PMU tests were designed or tested on anything
other than a PMUv3 (and probably not much interest to maintain the tests for
PMUv1 or v2 either). If do do this, may I suggest:
#if defined(__arm__)
if (pmu.version == ID_DFR0_PMU_V1 || pmu.version == ID_DFR0_PMU_V2)
return false;
#endif
That way the check is self documenting.
Thanks,
Alex
> /* PMUv3 requires an implementation includes some common events */
> required_events = is_event_supported(SW_INCR, true) &&
> is_event_supported(CPU_CYCLES, true) &&
> --
> 2.39.2
>
