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Re: [kvm-unit-tests PATCH v2 0/9] KVM: arm64: PMUv3 Event Counter Tests

From: Peter Maydell
Subject: Re: [kvm-unit-tests PATCH v2 0/9] KVM: arm64: PMUv3 Event Counter Tests
Date: Tue, 11 Feb 2020 15:42:38 +0000

On Thu, 30 Jan 2020 at 11:25, Eric Auger <address@hidden> wrote:
> This series implements tests exercising the PMUv3 event counters.
> It tests both the 32-bit and 64-bit versions. Overflow interrupts
> also are checked. Those tests only are written for arm64.
> It allowed to reveal some issues related to SW_INCR implementation
> (esp. related to 64-bit implementation), some problems related to
> 32-bit <-> 64-bit transitions and consistency of enabled states
> of odd and event counters (See [1]).
> Overflow interrupt testing relies of one patch from Andre
> ("arm: gic: Provide per-IRQ helper functions") to enable the
> PPI 23, coming from "arm: gic: Test SPIs and interrupt groups"
> (https://patchwork.kernel.org/cover/11234975/). Drew kindly
> provided "arm64: Provide read/write_sysreg_s".
> All PMU tests can be launched with:
> ./run_tests.sh -g pmu
> Tests also can be launched individually. For example:
> ./arm-run arm/pmu.flat -append 'chained-sw-incr'
> With KVM:
> - chain-promotion and chained-sw-incr are known to be failing.
>   [1] proposed a fix.
> - On TX2, I have some random failures due to MEM_ACCESS event
>   measured with a great disparity. This is not observed on
>   other machines I have access to.
> With TCG:
> - all new tests are skipped

I'm having a go at using this patchset to test the support
I'm adding for TCG for the v8.1 and v8.4 PMU extensions...

Q1: how can I get run_tests.sh to pass extra arguments to
QEMU ? The PMU events check will fail unless QEMU gets
the '-icount 8' to enable cycle-counting, but although
the underlying ./arm/run lets you add arbitrary extra
arguments to QEMU, run_tests.sh doesn't seem to. Trying to
pass them in via "QEMU=/path/to/qemu -icount 8" doesn't
work either.

Q2: do you know why arm/pmu.c:check_pmcr() insists that
PMCR.IMP is non-zero? The comment says "simple sanity check",
but architecturally a zero IMP field is permitted (meaning
"go look at MIDR_EL1 instead"). This causes TCG to fail this
test on '-cpu max', because in that case we set PMCR.IMP
to the same thing as MIDR_EL1.Implementer which is 0
("software use", since QEMU is software...)

-- PMM

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