On 2026/04/13 17:07, Akihiko Odaki wrote:
Assert the following:
- KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY is unset at initialization.
- KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY can be set.
- Setting KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY for the first time
   after setting an event filter results in EBUSY.
- KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY can be set again even if an
   event filter has already been set.
- Setting KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY after running a VCPU
   results in EBUSY.
- The existing test cases pass with
   KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY set.

Signed-off-by: Akihiko Odaki <[email protected]>
---
  .../selftests/kvm/arm64/vpmu_counter_access.c      | 147 +++++++++++++++++----
  1 file changed, 123 insertions(+), 24 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c 
b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
index ae36325c022f..6e2bf3ad63b2 100644
--- a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
+++ b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
@@ -403,12 +403,7 @@ static void create_vpmu_vm(void *guest_code)
  {
        struct kvm_vcpu_init init;
        uint8_t pmuver, ec;
-       uint64_t dfr0, irq = 23;
-       struct kvm_device_attr irq_attr = {
-               .group = KVM_ARM_VCPU_PMU_V3_CTRL,
-               .attr = KVM_ARM_VCPU_PMU_V3_IRQ,
-               .addr = (uint64_t)&irq,
-       };
+       uint64_t dfr0;
/* The test creates the vpmu_vm multiple times. Ensure a clean state */
        memset(&vpmu_vm, 0, sizeof(vpmu_vm));
@@ -434,8 +429,6 @@ static void create_vpmu_vm(void *guest_code)
        TEST_ASSERT(pmuver != ID_AA64DFR0_EL1_PMUVer_IMP_DEF &&
                    pmuver >= ID_AA64DFR0_EL1_PMUVer_IMP,
                    "Unexpected PMUVER (0x%x) on the vCPU with PMUv3", pmuver);
-
-       vcpu_ioctl(vpmu_vm.vcpu, KVM_SET_DEVICE_ATTR, &irq_attr);
  }
static void destroy_vpmu_vm(void)
@@ -461,15 +454,25 @@ static void run_vcpu(struct kvm_vcpu *vcpu, uint64_t 
pmcr_n)
        }
  }
-static void test_create_vpmu_vm_with_nr_counters(unsigned int nr_counters, bool expect_fail)
+static void test_create_vpmu_vm_with_nr_counters(unsigned int nr_counters,
+                                                bool fixed_counters_only,
+                                                bool expect_fail)
  {
        struct kvm_vcpu *vcpu;
        unsigned int prev;
        int ret;
+       uint64_t irq = 23;
create_vpmu_vm(guest_code);
        vcpu = vpmu_vm.vcpu;
+ if (fixed_counters_only)
+               vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                                    KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, 
NULL);
+
+       vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_IRQ, &irq);
+
        prev = get_pmcr_n(vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0)));
ret = __vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
@@ -489,15 +492,15 @@ static void test_create_vpmu_vm_with_nr_counters(unsigned 
int nr_counters, bool
   * Create a guest with one vCPU, set the PMCR_EL0.N for the vCPU to @pmcr_n,
   * and run the test.
   */
-static void run_access_test(uint64_t pmcr_n)
+static void run_access_test(uint64_t pmcr_n, bool fixed_counters_only)
  {
        uint64_t sp;
        struct kvm_vcpu *vcpu;
        struct kvm_vcpu_init init;
- pr_debug("Test with pmcr_n %lu\n", pmcr_n);
+       pr_debug("Test with pmcr_n %lu, fixed_counters_only %d\n", pmcr_n, 
fixed_counters_only);
- test_create_vpmu_vm_with_nr_counters(pmcr_n, false);
+       test_create_vpmu_vm_with_nr_counters(pmcr_n, fixed_counters_only, 
false);
        vcpu = vpmu_vm.vcpu;
/* Save the initial sp to restore them later to run the guest again */
@@ -531,14 +534,14 @@ static struct pmreg_sets validity_check_reg_sets[] = {
   * Create a VM, and check if KVM handles the userspace accesses of
   * the PMU register sets in @validity_check_reg_sets[] correctly.
   */
-static void run_pmregs_validity_test(uint64_t pmcr_n)
+static void run_pmregs_validity_test(uint64_t pmcr_n, bool fixed_counters_only)
  {
        int i;
        struct kvm_vcpu *vcpu;
        uint64_t set_reg_id, clr_reg_id, reg_val;
        uint64_t valid_counters_mask, max_counters_mask;
- test_create_vpmu_vm_with_nr_counters(pmcr_n, false);
+       test_create_vpmu_vm_with_nr_counters(pmcr_n, fixed_counters_only, 
false);
        vcpu = vpmu_vm.vcpu;
valid_counters_mask = get_counters_mask(pmcr_n);
@@ -588,11 +591,11 @@ static void run_pmregs_validity_test(uint64_t pmcr_n)
   * 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)
+static void run_error_test(uint64_t pmcr_n, bool fixed_counters_only)
  {
        pr_debug("Error test with pmcr_n %lu (larger than the host)\n", pmcr_n);
- test_create_vpmu_vm_with_nr_counters(pmcr_n, true);
+       test_create_vpmu_vm_with_nr_counters(pmcr_n, fixed_counters_only, true);
        destroy_vpmu_vm();
  }
@@ -622,22 +625,118 @@ static bool kvm_supports_nr_counters_attr(void)
        return supported;
  }
+static void test_config(uint64_t pmcr_n, bool fixed_counters_only)
+{
+       uint64_t i;
+
+       for (i = 0; i <= pmcr_n; i++) {
+               run_access_test(i, fixed_counters_only);
+               run_pmregs_validity_test(i, fixed_counters_only);
+       }
+
+       for (i = pmcr_n + 1; i < ARMV8_PMU_MAX_COUNTERS; i++)
+               run_error_test(i, fixed_counters_only);
+}
+
+static void test_fixed_counters_only(uint64_t pmcr_n)
+{
+       struct kvm_pmu_event_filter filter = { .nevents = 0 };
+       struct kvm_vm *vm;
+       struct kvm_vcpu *running_vcpu;
+       struct kvm_vcpu *stopped_vcpu;
+       struct kvm_vcpu_init init;
+       int ret;
+       uint64_t irq = 23;
+
+       create_vpmu_vm(guest_code);
+       ret = __vcpu_has_device_attr(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                                    KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY);
+       if (ret) {
+               TEST_ASSERT(ret == -1 && errno == ENXIO,
+                           KVM_IOCTL_ERROR(KVM_HAS_DEVICE_ATTR, ret));
+               destroy_vpmu_vm();
+               return;
+       }
+
+       /* Assert that FIXED_COUNTERS_ONLY is unset at initialization. */
+       ret = __vcpu_device_attr_get(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                                    KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, 
NULL);
+       TEST_ASSERT(ret == -1 && errno == ENXIO,
+                   KVM_IOCTL_ERROR(KVM_GET_DEVICE_ATTR, ret));
+
+       /* Assert that setting FIXED_COUNTERS_ONLY succeeds. */
+       vcpu_device_attr_set(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, NULL);
+
+       /* Assert that getting FIXED_COUNTERS_ONLY succeeds. */
+       vcpu_device_attr_get(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, NULL);
+
+       /*
+        * Assert that setting FIXED_COUNTERS_ONLY again succeeds even if an
+        * event filter has already been set.
+        */
+       vcpu_device_attr_set(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_FILTER, &filter);
+
+       vcpu_device_attr_set(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, NULL);
+
+       destroy_vpmu_vm();
+
+       create_vpmu_vm(guest_code);
+
+       /*
+        * Assert that setting FIXED_COUNTERS_ONLY results in EBUSY if an event
+        * filter has already been set while FIXED_COUNTERS_ONLY has not.
+        */
+       vcpu_device_attr_set(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_FILTER, &filter);
+
+       ret = __vcpu_device_attr_set(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                                    KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, 
NULL);
+       TEST_ASSERT(ret == -1 && errno == EBUSY,
+                   KVM_IOCTL_ERROR(KVM_SET_DEVICE_ATTR, ret));
+
+       destroy_vpmu_vm();
+
+       /*
+        * Assert that setting FIXED_COUNTERS_ONLY after running a VCPU results
+        * in EBUSY.
+        */
+       vm = vm_create(2);
+       vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &init);
+       init.features[0] |= (1 << KVM_ARM_VCPU_PMU_V3);
+       running_vcpu = aarch64_vcpu_add(vm, 0, &init, guest_code);
+       stopped_vcpu = aarch64_vcpu_add(vm, 1, &init, guest_code);
+       kvm_arch_vm_finalize_vcpus(vm);
+       vcpu_device_attr_set(running_vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_IRQ, &irq);
+       vcpu_device_attr_set(running_vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                            KVM_ARM_VCPU_PMU_V3_INIT, NULL);
+       run_vcpu(running_vcpu, pmcr_n);

Sorry, I sent a series before testing by mistake. This hangs the test and I'll send a fix later. Anything else is fine and ready for review.

Regards,
Akihiko Odaki

+
+       ret = __vcpu_device_attr_set(stopped_vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+                                    KVM_ARM_VCPU_PMU_V3_FIXED_COUNTERS_ONLY, 
NULL);
+       TEST_ASSERT(ret == -1 && errno == EBUSY,
+                   KVM_IOCTL_ERROR(KVM_SET_DEVICE_ATTR, ret));
+
+       kvm_vm_free(vm);
+
+       test_config(0, true);
+}
+
  int main(void)
  {
-       uint64_t i, pmcr_n;
+       uint64_t pmcr_n;
TEST_REQUIRE(kvm_has_cap(KVM_CAP_ARM_PMU_V3));
        TEST_REQUIRE(kvm_supports_vgic_v3());
        TEST_REQUIRE(kvm_supports_nr_counters_attr());
pmcr_n = get_pmcr_n_limit();
-       for (i = 0; i <= pmcr_n; i++) {
-               run_access_test(i);
-               run_pmregs_validity_test(i);
-       }
-
-       for (i = pmcr_n + 1; i < ARMV8_PMU_MAX_COUNTERS; i++)
-               run_error_test(i);
+       test_config(pmcr_n, false);
+       test_fixed_counters_only(pmcr_n);
return 0;
  }



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