[PATCH v3 17/57] KVM: selftests: Update x86's KVM PV test to match KVM's disabling exits behavior

[Sean Christopherson]

Rework x86's KVM PV features test to align with KVM's new, fixed behavior
of not allowing userspace to disable HLT-exiting after vCPUs have been
created.  Rework the core testcase to disable HLT-exiting before creating
a vCPU, and opportunistically modify keep the paired VM+vCPU creation to
verify that KVM rejects KVM_CAP_X86_DISABLE_EXITS as expected.

Reviewed-by: Maxim Levitsky <mlevi...@redhat.com>
Signed-off-by: Sean Christopherson <sea...@google.com>
---
 .../selftests/kvm/x86_64/kvm_pv_test.c        | 33 +++++++++++++++++--
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c 
b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
index 2aee93108a54..1b805cbdb47b 100644
--- a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
@@ -139,6 +139,7 @@ static void test_pv_unhalt(void)
        struct kvm_vm *vm;
        struct kvm_cpuid_entry2 *ent;
        u32 kvm_sig_old;
+       int r;
 
        if (!(kvm_check_cap(KVM_CAP_X86_DISABLE_EXITS) & 
KVM_X86_DISABLE_EXITS_HLT))
                return;
@@ -152,19 +153,45 @@ static void test_pv_unhalt(void)
        TEST_ASSERT(vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
                    "Enabling X86_FEATURE_KVM_PV_UNHALT had no effect");
 
-       /* Make sure KVM clears vcpu->arch.kvm_cpuid */
+       /* Verify KVM disallows disabling exits after vCPU creation. */
+       r = __vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, 
KVM_X86_DISABLE_EXITS_HLT);
+       TEST_ASSERT(r && errno == EINVAL,
+                   "Disabling exits after vCPU creation didn't fail as 
expected");
+
+       kvm_vm_free(vm);
+
+       /* Verify that KVM clear PV_UNHALT from guest CPUID. */
+       vm = vm_create(1);
+       vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
+
+       vcpu = vm_vcpu_add(vm, 0, NULL);
+       TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
+                   "vCPU created with PV_UNHALT set by default");
+
+       vcpu_set_cpuid_feature(vcpu, X86_FEATURE_KVM_PV_UNHALT);
+       TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
+                   "PV_UNHALT set in guest CPUID when HLT-exiting is 
disabled");
+
+       /*
+        * Clobber the KVM PV signature and verify KVM does NOT clear PV_UNHALT
+        * when KVM PV is not present, and DOES clear PV_UNHALT when switching
+        * back to the correct signature..
+        */
        ent = vcpu_get_cpuid_entry(vcpu, KVM_CPUID_SIGNATURE);
        kvm_sig_old = ent->ebx;
        ent->ebx = 0xdeadbeef;
        vcpu_set_cpuid(vcpu);
 
-       vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
+       vcpu_set_cpuid_feature(vcpu, X86_FEATURE_KVM_PV_UNHALT);
+       TEST_ASSERT(vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
+                   "PV_UNHALT cleared when using bogus KVM PV signature");
+
        ent = vcpu_get_cpuid_entry(vcpu, KVM_CPUID_SIGNATURE);
        ent->ebx = kvm_sig_old;
        vcpu_set_cpuid(vcpu);
 
        TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
-                   "KVM_FEATURE_PV_UNHALT is set with 
KVM_CAP_X86_DISABLE_EXITS");
+                   "PV_UNHALT set in guest CPUID when HLT-exiting is 
disabled");
 
        /* FIXME: actually test KVM_FEATURE_PV_UNHALT feature */
 
-- 
2.47.0.338.g60cca15819-goog