Re: [PATCH v5 10/12] KVM: selftests: aarch64: Introduce vpmu_counter_access test

[Raghavendra Rao Ananta]

Hi Oliver,

On Fri, Sep 15, 2023 at 2:00 PM Oliver Upton <oliver.upton@xxxxxxxxx> wrote:
>
> Hi Raghu,
>
> On Thu, Aug 17, 2023 at 12:30:27AM +0000, Raghavendra Rao Ananta wrote:
> > From: Reiji Watanabe <reijiw@xxxxxxxxxx>
> >
> > Introduce vpmu_counter_access test for arm64 platforms.
> > The test configures PMUv3 for a vCPU, sets PMCR_EL0.N for the vCPU,
> > and check if the guest can consistently see the same number of the
> > PMU event counters (PMCR_EL0.N) that userspace sets.
> > This test case is done with each of the PMCR_EL0.N values from
> > 0 to 31 (With the PMCR_EL0.N values greater than the host value,
> > the test expects KVM_SET_ONE_REG for the PMCR_EL0 to fail).
> >
> > Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
> > Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> > ---
> >  tools/testing/selftests/kvm/Makefile          |   1 +
> >  .../kvm/aarch64/vpmu_counter_access.c         | 235 ++++++++++++++++++
> >  2 files changed, 236 insertions(+)
> >  create mode 100644 tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
> >
> > diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> > index c692cc86e7da8..a1599e2b82e38 100644
> > --- a/tools/testing/selftests/kvm/Makefile
> > +++ b/tools/testing/selftests/kvm/Makefile
> > @@ -148,6 +148,7 @@ TEST_GEN_PROGS_aarch64 += aarch64/smccc_filter
> >  TEST_GEN_PROGS_aarch64 += aarch64/vcpu_width_config
> >  TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
> >  TEST_GEN_PROGS_aarch64 += aarch64/vgic_irq
> > +TEST_GEN_PROGS_aarch64 += aarch64/vpmu_counter_access
> >  TEST_GEN_PROGS_aarch64 += access_tracking_perf_test
> >  TEST_GEN_PROGS_aarch64 += demand_paging_test
> >  TEST_GEN_PROGS_aarch64 += dirty_log_test
> > diff --git a/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c b/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
> > new file mode 100644
> > index 0000000000000..d0afec07948ef
> > --- /dev/null
> > +++ b/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
> > @@ -0,0 +1,235 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * vpmu_counter_access - Test vPMU event counter access
> > + *
> > + * Copyright (c) 2022 Google LLC.
> > + *
> > + * This test checks if the guest can see the same number of the PMU event
> > + * counters (PMCR_EL0.N) that userspace sets.
> > + * This test runs only when KVM_CAP_ARM_PMU_V3 is supported on the host.
> > + */
> > +#include <kvm_util.h>
> > +#include <processor.h>
> > +#include <test_util.h>
> > +#include <vgic.h>
> > +#include <perf/arm_pmuv3.h>
> > +#include <linux/bitfield.h>
> > +
> > +/* The max number of the PMU event counters (excluding the cycle counter) */
> > +#define ARMV8_PMU_MAX_GENERAL_COUNTERS       (ARMV8_PMU_MAX_COUNTERS - 1)
> > +
> > +struct vpmu_vm {
> > +     struct kvm_vm *vm;
> > +     struct kvm_vcpu *vcpu;
> > +     int gic_fd;
> > +};
> > +
>
> nit: this test is single threaded, so there will only ever be a single
> instance of a VM at a time. Dynamically allocating a backing structure
> doesn't add any value, IMO.
>
> You can just get away with using globals.
>
Probably. I can try to have a single global.

> > +/*
> > + * Create a guest with one vCPU, and attempt to set the PMCR_EL0.N for
> > + * the vCPU to @pmcr_n, which is larger than the host value.
> > + * The attempt should fail as @pmcr_n is too big to set for the vCPU.
> > + */
> > +static void run_error_test(uint64_t pmcr_n)
> > +{
> > +     struct vpmu_vm *vpmu_vm;
> > +     struct kvm_vcpu *vcpu;
> > +     int ret;
> > +     uint64_t pmcr, pmcr_orig;
> > +
> > +     pr_debug("Error test with pmcr_n %lu (larger than the host)\n", pmcr_n);
> > +     vpmu_vm = create_vpmu_vm(guest_code);
> > +     vcpu = vpmu_vm->vcpu;
> > +
> > +     /* Update the PMCR_EL0.N with @pmcr_n */
> > +     vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0), &pmcr_orig);
> > +     pmcr = pmcr_orig & ~ARMV8_PMU_PMCR_N;
> > +     pmcr |= (pmcr_n << ARMV8_PMU_PMCR_N_SHIFT);
> > +
> > +     /* This should fail as @pmcr_n is too big to set for the vCPU */
> > +     ret = __vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0), pmcr);
> > +     TEST_ASSERT(ret, "Setting PMCR to 0x%lx (orig PMCR 0x%lx) didn't fail",
> > +                 pmcr, pmcr_orig);
>
> The failure pattern for this should now be the write to PMCR_EL0.N had
> no effect.
>
Right. I'll make the change.

Thank you.
Raghavendra
> --
> Thanks,
> Oliver