Re: [RFC PATCH v3 29/29] KVM: arm64: selftests: Introduce id_reg_test

[Reiji Watanabe <reijiw@google.com>]

Hi Eric,

> >> After fixing the mem_pages stuff I get the following error on a cavium
> >> machine.
> >>
> >> augere@virtlab-arm04:~/UPSTREAM/ML/tools/testing/selftests/kvm#
> >> ./aarch64/id_reg_test
> >> ==== Test Assertion Failure ====
> >>   aarch64/id_reg_test.c:814: fval >= min
> >>   pid=11692 tid=11692 errno=4 - Interrupted system call
> >>      1  0x00000000004028d3: test_feature at id_reg_test.c:813
> >>      2   (inlined by) test_feature_all at id_reg_test.c:863
> >>      3   (inlined by) run_test at id_reg_test.c:1073
> >>      4  0x000000000040156f: main at id_reg_test.c:1124
> >>      5  0x000003ffa9420de3: ?? ??:0
> >>      6  0x00000000004015eb: _start at :?
> >>   PERFMON field of ID_DFR0 is too small (0)
> >>
> >> Fails on
> >> test_feature: PERFMON (reg ID_DFR0)
> >>
> >> I will do my utmost to further debug
> >
> > Thank you for running it in your environment and reporting this !
> > This is very interesting...
> >
> > It implies that the host's ID_DFR0_EL1.PerfMon is zero or 0xf
> > (meaning FEAT_PMUv3 is not implemented) even though the host's
> > ID_AA64DFR0_EL1.PMUVer indicates that FEAT_PMUv3 is implemented.
> >
> > Would it be possible for you to check values of those two
> > registers on the host (not on the guest) to see if both of them
> > indicate the presence of FEAT_PMUv3 consistently ?
>
> Here are both values printed in armpmu_register()
> [   33.320901] armpmu_register perfmon=0x0 pmuver=0x4
>
>         perfmon =
> cpuid_feature_extract_unsigned_field(read_cpuid(ID_DFR0_EL1),
>                         ID_DFR0_PERFMON_SHIFT);
>         pmuver =
> cpuid_feature_extract_unsigned_field(read_cpuid(ID_AA64DFR0_EL1),
>                         ID_AA64DFR0_PMUVER_SHIFT);
>         printk("%s perfmon=0x%x pmuver=0x%x\n", __func__, perfmon, pmuver);
>
> My machine is a Gigabyte R181-T90 (ThunderX2)

Thank you for your providing the information !!

Since the test incorrectly expects that ID_DFR0_EL1.PerfMon indicates
PMUv3 on any CPUs that support PMUv3 even when they don't support
32bit EL0, I will fix the test.
(ThunderX2 doesn't seem to support 32bit EL0)

Thanks,
Reiji