KVM: selftests: Extend cpuid_test to verify KVM_GET_CPUID2 "nent" updates

Verify that KVM reports the actual number of CPUID entries on success, but
doesn't touch the userspace struct on failure (which for better or worse,
is KVM's ABI).

Link: https://lore.kernel.org/r/20230526210340.2799158-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/x86_64/cpuid_test.c b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
index 2fc3ad9c887e2aa7ac306cf7ddd7a8ba60c5d2c5..d3c3aa93f0903545e23b7f4ba3acedf4fd77526b 100644 (file)
--- a/tools/testing/selftests/kvm/x86_64/cpuid_test.c
+++ b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
@@ -163,6 +163,25 @@ static void set_cpuid_after_run(struct kvm_vcpu *vcpu)
        ent->eax = eax;
 }
 
+static void test_get_cpuid2(struct kvm_vcpu *vcpu)
+{
+       struct kvm_cpuid2 *cpuid = allocate_kvm_cpuid2(vcpu->cpuid->nent + 1);
+       int i, r;
+
+       vcpu_ioctl(vcpu, KVM_GET_CPUID2, cpuid);
+       TEST_ASSERT(cpuid->nent == vcpu->cpuid->nent,
+                   "KVM didn't update nent on success, wanted %u, got %u\n",
+                   vcpu->cpuid->nent, cpuid->nent);
+
+       for (i = 0; i < vcpu->cpuid->nent; i++) {
+               cpuid->nent = i;
+               r = __vcpu_ioctl(vcpu, KVM_GET_CPUID2, cpuid);
+               TEST_ASSERT(r && errno == E2BIG, KVM_IOCTL_ERROR(KVM_GET_CPUID2, r));
+               TEST_ASSERT(cpuid->nent == i, "KVM modified nent on failure");
+       }
+       free(cpuid);
+}
+
 int main(void)
 {
        struct kvm_vcpu *vcpu;
@@ -183,5 +202,7 @@ int main(void)
 
        set_cpuid_after_run(vcpu);
 
+       test_get_cpuid2(vcpu);
+
        kvm_vm_free(vm);
 }