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

Oliver Upton
2023-09-15T21:01:51Z

Hi Raghu,

On Thu, Aug 17, 2023 at 12:30:27AM +0000, Raghavendra Rao Ananta wrote:
> From: Reiji Watanabe <reijiw@google.com>
>
> 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@google.com>
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> ---
> 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.

> +/*
> + * 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.

--
Thanks,
Oliver