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

From: Andrew Jones
Subject: Re: [kvm-unit-tests PATCH v2 0/9] KVM: arm64: PMUv3 Event Counter Tests
Date: Tue, 11 Feb 2020 17:07:33 +0100

On Tue, Feb 11, 2020 at 03:42:38PM +0000, Peter Maydell wrote:
> 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.

Alex Bennee once submit a patch[*] allowing that to work, but
it never got merged. I just rebased it and tried it, but it
doesn't work now. Too much has changed in the run scripts
since his posting. I can try to rework it though.


> 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...)

Probably just a misunderstanding on the part of the author (and
reviewers). Maybe Eric can fix that while preparing this series.


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